2.    The ideal inverting amplifier with the input signal is applied in the inverting input terminal and ground while the non inverting input connected to the ground. Two resistors are connected in the circuit in such that a resistor feeds the input signal while another resistor between the output and Inverting input terminals. Here when the input signal is positive the output will be negative and vice versa. The voltage change at the output relative to the input depends on the ratio of the resistors.Therefore the voltage gain is R2/R1.

 

3.    Virtual ground is a concept that is very useful in analysis of Op-Amp circuits and it will make  the calculations very simple. The voltage at that particular node is almost equal to ground voltage which is 0V.

 

4.    The significance of a zero output resistance is to make the op-amp to have zero voltage so that the maximum voltage will be transferred to the output load. Voltage is divided in a circuit according to the amount of resistance present in a circuit. In order for the voltage to drop across the output load, that load must be of greater resistance than the output of the op-amp.

 

5.    The ideal summing amplifier enable to add many signals together. These input signals are given to the inverting terminal of the operational amplifier using input resistors. Non-inverting terminal of the operational amplifier is given to the ground terminal using a resistor.A feedback resistor is placed between input inverting and output terminals. The resulting output will be the sum of all the input voltages applied but inverted. So, the formula to find the output voltage is VOUT = – (Rf/RIN) VIN

 

6.    The ideal non inverting amplifier has the non inverting input receives the signal while the Inverting input is connected with ground.The feedback resistor connected between output and inverting input terminals. When the input signal moves either positive or negative, the output will be in same phase.The voltage gain in this case will be always higher than 1 so (1+R2/R1).

 

7.    Voltage follower is a Op-Amp which has a voltage gain of 1.This means that the op amp does not provide any amplification to the signal. The reason it is called a voltage follower is because the output voltage directly follows the input voltage, meaning the output voltage is the same as the input voltage. The advantage of voltage follower is that its input resistance is very large and output resistance is very small,so it can be used as buffer circuit. The buffer is used to avoid the loading effect on the circuit.

1. Ideal Op-Amp model has infinite input impedance and zero output impedance. The resistance at both input terminals is infinite therefore the current in each input lead is said to be zero. The output voltage is independent of the output current as the voltage gain is independent of the output current so it can be said that the output resistance is zero.

2. In an ideal inverting amplifier, the input signal is applied through resistor to the inverting Op-Amp input. The feedback resistor connects from the the output to the inverting input. The circuit is called an inverting amplifier because its voltage gain is negative. This means that if the input voltage is increasing or going positive, the output voltage will be decreasing or going negative, and vice versa. 

3. The virtual ground means that the voltage at that particular node is almost equal to ground voltage which is 0V. However, it is not physically connected to ground.

4. Once the voltage is dropped across the Op-Amp and it does its task of amplifying the signal, the signal should get dropped across the device that the Op-Amp should feed. Therefore, Op-Amp needs low output impedance, so that it can drop its amplified voltage signals across the desired device effectively and not on itself.

5. An ideal summing amplifier is another type of operational amplifier circuit configuration that is used to combine the voltages present on two or more inputs into a single output voltage. These amplifiers are used in an audio mixer to add different signals with equal gains. There are various resistors are used at the input of the summing amplifier to give a weighted sum. This can be used to change a binary number to a voltage in an AC (digital to analog converter). This amplifier is used to apply a DC offset voltage with an AC signal voltage. 

6. Input voltage is applied to the non-inverting Op-Amp input. A voltage divider consisting of feedback resistors and another resistor connects from the output node to the inverting input. The circuit is called a non-inverting amplifier because its voltage gain is positive. This means that if the input voltage is increasing or going positive, the output voltage will also be increasing or going positive. 

7. The voltage follower or unity-gain buffer is a unity-gain non-inverting amplifier. Compared to the non-inverting amplifier, the feedback resistor is replaced by a short circuit and resistor is omitted. The advantage of using this circuit is it is said to have 100% feedback as the output node is connected directly to the inverting input instead of through a voltage divider. Therefore, the circuit has unity voltage gain. The voltage follower is often used to isolate a low resistance load from a high output resistance source. Due to that, the voltage follower supplies the current to drive the load while drawing no current from the input circuit. 

 

1. Ideal op-amp model has infinite open loop voltage gain, infinite input impedance ,zero output impedance and infinite bandwidth. The input currents and voltages will be zero. 

2. Inverting Amplifier is a normal OP-Amp in which the output is given as feedback to the inverted terminal of input by means of a feedback resistor. We apply a resistance between negative terminal of op amp and output terminal. this resistance is called negative feedback resistance that is represented by R with subscript f. 

3. Virtual ground means that the voltage at that particular node is almost equal to ground voltage (0V). It is not physically connected to ground. 

4. Low impedance in a voltage source is usually preferred because it helps to keep out the noise out of the circuit and maintain a stable output voltage. 

5. If we add more input resistors to the input, each equal in value to the original input resistor, (RIN) we end up with another operational amplifier circuit called summing amplifier. 

6. In this circuit the signal is applied to the non-inverting input of the op-amp. In this way the signal at the output is not inverted when compared to the input. However the feedback is taken from the output of the op-amp via a resistor to the inverting input of the operational amplifier where another resistor is taken to ground. It has to be applied to the inverting input as it is negative feedback. It is the value of these two resistors that govern the gain of the operational amplifier circuit as they determine the level of feedback. 

7. A voltage follower (also called a unity-gain amplifier, a buffer amplifier, and an isolation amplifier) is a op-amp circuit which has a voltage gain of 1. This means that the op amp does not provide any amplification to the signal. The reason it is called a voltage follower is because the output voltage directly follows the input voltage, meaning the output voltage is the same as the input voltage. When a circuit has high input impedance , very little current is drawn from the circuit. If you are familiar with ohm’s law, you’ll know that I=V/R. Thus, greater the resistance, less current is drawn from the source. The power of the circuit is not affected when current is feeding a high impedance load. 

Discussion Questions 

1. Describe the ideal Op-Amp model and describe the implications of this ideal model in terms of input currents and voltages. 

Op-Amp is an analog integrated circuit that can perform many mathematical operations. It has two input terminals and one output terminal. The input terminals are called as inverting input terminal and non-inverting input terminal. Op-Amp also need power supply to operate. Both positive and negative power supply are used simultaneously. Input resistance of Op-Amp is infinity while output resistance is 0. At the close-loop operation, inverting input terminal is virtual ground. There should be no change in output voltage for any amount of voltage applied between those two shorted inputs and ground. 

 

2. Describe the operation and characteristics of the ideal inverting amplifier. 

Inverting amplifier makes a 180 degree phase difference between input and output signals. The benefit of this amplifier is that its gain does not depend on the active component parameter but it depends on the passive component. Therefore, the gain of the amplifier is highly stable. According to Miller’s theorem, if the voltage gain of the amplifier is infinite then this close-loop amplifier’s inverting input terminal acts as a virtual ground where the potential of this point is zero with respect to ground but actually it does not connect to the ground physically. 

 

3. What is the concept of virtual ground? 

A virtual ground is a node of a circuit that is maintained at a steady reference potential without connected directly to the reference potential. In some cases the reference potential is considered to be that of the surface of the earth where the reference node is called "ground" or "earth" as a consequence. This concept helps circuit analysis in operational amplifier and other circuits as well as provides useful practical circuit effects that would be difficult to achieve in any other ways. A node may have any value of current or voltage but physical implementations of a virtual ground will have limitations of current handling ability and a non-zero impedance which may have practical side effects. 

 

4. What is the significance of a zero output resistance? 

A low resistance means that the circuit draws or provides more power on the signal. Input resistance must be higher than output resistance. Input is only capable to provide power to output. If input resistance is lower than output resistance, input voltage will be dropped. Zero output resistance can provide the correct voltage level on the signal and the signal will be read correctly. Low impedance in a voltage source is usually preferred because it helps to keep out the noise out of the circuit and maintain a stable output voltage. 

 

5. Describe the operation  and characteristics of the ideal summing amplifier 

The output of the amplifier is the function of summation of the input voltages. The circuit can be done based on virtual ground or Kirchhoff current low. A summing amplifier sums several weighted voltage. Output is inverted. 

 

6. Describe the operation and characteristics of the ideal non inverting amplifier 

The input and output signals are in the same phase. The benefit of this amplifier is that its gain does not depend on the active component parameter but passive component parameter which cause the gain of amplifier is infinite. If the voltage gain of amplifier is infinite, the close-loop amplifier inverting inverting input terminal acts as virtual ground. The potential of this point is zero with respect to the ground but physically not connected to the ground. Assume that no current enters the input terminal since the ideal op-amp input resistance is infinite. 

 
 

7. Describe the voltage follower. what are the advantages of using this circuit. 

In a voltage follower the output voltage is equal to the input voltage. The advantage of this circuit is that the op-amp can provide current and power gain. It also has very large input resistance and very small output resistance which can be used as an impedance transformer or buffer circuit. The op-amp draws almost no current from the input. It provides low output impedance to any circuit using the output of the follower where the output will not drop under load. 

NURUL NAJIHAH BINTI BAKAR (1813424)

An ideal op amp is an op amp that has perfect conditions to allow it to function as an op amp with 100% efficiency. The ideal op-amp has infinite voltage gain,infinite bandwidth,infinite input impedance and zero output impedance.The implications of this ideal model in terms of input currents and voltages is the output attempts to do whatever is necessary to make the voltage difference between the inputs zero which applies only to closed-loop amplifier circuits, means that the feedback sent from the output to the input causes the two input voltages to become the same. Then, the input draws no current. This means that the input terminals look at the voltage placed across them but do not allow any current to flow into the op amp.

The ideal inverting amplifier is the output is inverted with respect to input. The voltage gain can be adjusted as greater than equal to or less than one. The input impedance is R1. The op-amp input resistance is large,so the current into the positive terminal and negative terminal op-amp inputs terminal will be small,essentially zero.

The term virtual ground means that the voltage at that particular node is almost equal to ground voltage (0 v). It is not physically connected to ground. A virtual ground is a node of a circuit that is maintained at a steady reference potential, without being connected directly to the reference potential. The virtual ground concept aids circuit analysis in operational amplifier and other circuits and provides useful practical circuit effects that would be difficult to achieve in other ways.

An ideal op amp will have zero output impedance. When an op amp produces its output signal, the op amp will  have zero voltage so that the maximum voltage will be transferred to the output load. Voltage is divided in a circuit according to the amount of impedance present in a circuit. Voltage drops across a component of higher impedance. In order for the voltage to drop across the output load, that load must be of greater impedance than the output of the op amp.

The term summing amplifier is also named as adder, which is used to add two signal voltages. Summing amplifier is an amplifier that adds different inputs provided at inverting or non-inverting input terminals.It is highly used when we need to add different inputs. The output of the amplifier is the function of summation of the input voltages. The circuit analysis is done based on virtual ground and Kirchhoff current law (kcl).

6. Describe the operation and characteristics of the ideal non inverting amplifier

The ideal non-inverting amplifier is no phase shift between input and output. The voltage gain is always greater than one. The input impedance is very large. The input resistance to the non-inverting amplifier is very high because the input current to the amplifier is also the input current to the op-amp which must be extremely small.

A voltage follower is also called a unity-gain amplifier, a buffer amplifier, and an isolation amplifier which has a voltage gain of 1.This means that the op-amp does not provide any amplification to the signal. The reason it is called a voltage follower is because the output voltage directly follows the input voltage, meaning the output voltage is the same as the input voltage.The advantages are the input resistance  is very large and output resistance is very small, so it can be used as an impedance transformer or buffer circuit.The impedance transformer or buffer is used to avoid the loading effect on the circuit.

 

2. Describe the operation and characteristics of the ideal inverting amplifier.

 

3. What is the concept of virtual ground?

4. What is the significance of a zero output resistance?

5. Describe the operation  and characteristics of the ideal summing amplifier

6. Describe the operation and characteristics of the ideal non inverting amplifier

7. Describe the voltage follower. what are the advantages of using this circuit.

 

-Open loop gain is the gain of the Op Amp without a positive or negative feedback. An ideal OP Amp should have an infinite open loop gain but typically it range between 20,000 and 2, 00000. 

-Input impedence. It is the ratio of the input voltage to input current. It should be infinite without any leakage of current from the supply to the inputs. But there will be a few Pico ampere current leakages in most Op Amps.

-The ideal Op Amp should have zero output impedance without any internal resistance. So that it can supply full current to the load connected to the output.

-The ideal Op Amp should have an infinite frequency response so that it can amplify any frequency from DC signals to the highest AC frequencies. But most Op Amps have limited bandwidth.

-The output of the Op Amp should be zero when the voltage difference between the inputs is zero. But in most Op Amps, the output will not be zero when off but there will be a minute voltage from it.

2) Inverting amplifier.

Negative Feedback is the process of feeding back a fraction of the output signal back to the input, but to make the feedback negative, we must feed it back to the negative or inverting input terminal of the op-amp using an external Feedback Resisto. This feedback connection between the output and the inverting input terminal forces the differential input voltage towards zero.

This effect produces a closed loop circuit to the amplifier resulting in the gain of the amplifier now being called its Closed-loop Gain. Then a closed-loop inverting amplifier uses negative feedback to accurately control the overall gain of the amplifier, but at a cost in the reduction of the amplifiers gain.

This negative feedback results in the inverting input terminal having a different signal on it than the actual input voltage as it will be the sum of the input voltage plus the negative feedback voltage giving it the label or term of a Summing Point. We must therefore separate the real input signal from the inverting input by using an Input Resistor.

3) Virtual ground.

The term virtual ground means that the voltage at that particular node is almost equal to ground voltage (0V). It is not physically connected to ground. This concept is very useful in analysis of op amp circuits and it will make a lot of calculations very simple.

4) Zero output resistance.

The output impedance of the ideal operational amplifier is assumed to be zero acting as a perfect internal voltage source with no internal resistance so that it can supply as much current as necessary to the load. This internal resistance is effectively in series with the load thereby reducing the output voltage available to the load. Real op-amps have output impedances in the 100-20kΩ range.

5) Summing Amplifier

Combine the voltages present on two or more inputs into a single output voltage. The operation is when more input resistors are added to the input terminal. The summing amplifier able to take almost unlimited number of inputs and none of one input should appear on another input.

       6)  Non inverting amplifier

Non-Inverting amplifier is one in which the output is in phase with respect to the input. The feedback is applied at the inverting input. However, the input is now applied at the non-inverting input. The output is a non-Inverted amplified version of input. The gain of the non-inverting amplifier circuit for the operational amplifier is easy to determine. This arises from the fact that the gain of the amplifier is exceedingly high. If the output of the circuit remains within the supply rails of the amplifier, then the output voltage divided by the gain means that there is virtually no difference between the two inputs.

        7)  Voltage Follower

A voltage follower also called a unity-gain amplifier, a buffer amplifier, and an isolation amplifier is a op-amp circuit which has a voltage gain of 1.

This means that the op amp does not provide any amplification to the signal. The reason it is called a voltage follower is because the output voltage directly follows the input voltage, meaning the output voltage is the same as the input voltage. Thus, for example, if 10V goes into the op amp as input, 10V comes out as output. A voltage follower acts as a buffer, providing no amplification or attenuation to the signal.

      

      

1. The ideal Op-Amp model is the voltage gain is infinite, infinitely high input impedence, almost zero output impedence, the model mostly has two input terminal and one output terminal and lastly use dual power supplies which positive and negative terminal.

As for implications, the amplifier will draws no current and the voltage difference between inputs is zero.

2. Operation and characteristic of ideal inverting amplifier.

The input is connected directly to the inverting end of the Op-Amp causing the output voltage is 180 degree compared to input.

3.  Concept virtual ground

If one terminal is at the ground potential, the other terminal will appear to be at ground potential as well although they are not physically grounded

4. Significance of zero output resistance

The load will not cause the voltage to drop at the output and thus the load can get sufficient power to operate properly

5. Operation and characteristic of ideal summing amplifier

Summing amplifier is applying multiple inputs to either inverting or non-inverting terminal Op-Amp

6. Operation and characteristic of ideal non-inverting amplifier

The input voltage, Vi is connected directly to the non-inverting which is + terminal and thus creating the exact same signal as the input (signal not inverted)

Characteristic : high input impedence is required

7. Voltage follower

Input signal is applied directly to non-inverting input of amplifier. Then the output signal will not inverted and thus the output voltage is the same as input voltage, Vout = Vin.

Advantages

Impedence  matching or circuit isolation is more vital compared to amplifier because it maintains the signal voltage.

 

1. Describe the ideal Op-Amp model and describe the implications of this ideal model in terms of input currents and voltages.
-The op-amp has one output terminal and two input terminals, called inverting input terminal and non-inverting input terminal. The op-amp also needs power supply for its operation and generally both positive and negative power supply are used simultaneously.
-Input resistance is infinity, open-loop differential mode voltage gain is infinity, open-loop common mode voltage gain is 0, gain bandwidth product is infinity, common mode rejection ratio is infinity, output resistance is 0. At close-loop operation, inverting input terminal is virtual ground.
- Since the input resistance is infinity, the input current is 0.
-Vo = Av ( V2 – V1), V1=V2 and make the open loop gain infinity.

2. Describe the operation and characteristics of the ideal inverting amplifier.
-Input signal is applied in the inverting input terminal and ground. The non-inverting terminal is connected to the ground. The feedback resistor is connected between the output and inverting input terminals. The inverting amplifier makes a 180 phase difference between input and output signals. 
-The main benefit of this amplifier is that its gain does not depend on the active component parameter but depends on the passive component, so the gain of the amplifier is highly stable. According to Miller’s theorem, if the voltage gain of the amplifier is infinite, then this close-loop amplifier’s inverting input terminal acts as a virtual ground, that is the potential of this point is zero with respect to the ground, but physically it does not connect to the ground.
-Input resistance is infinity, input current = 0. 

 

3. What is the concept of virtual ground?
-As the name indicates it is virtual, not real ground. It is considered as equivalent to ground. The term virtual ground means that the voltage at that particular node is almost equal to ground voltage (0V). It is not physically connected to ground.

4. What is the significance of a zero output resistance?
-The output resistance of the ideal operational amplifier is assumed to be zero acting as a perfect internal voltage source with no internal resistance so that it can supply the maximum current to the load. This internal resistance is effectively in series with the load thereby reducing the output voltage available to the load. 

5. Describe the operation  and characteristics of the ideal summing amplifier
-The output of the amplifier is the function of the summation of the input voltages. To simplify the analysis, only three input signals are arbitrarily selected. The circuit analysis is done based on virtual ground and Kirchhoff current low.
-The close-loop amplifier inverting input terminal act as virtual ground.
-The input resistance is infinity, the input current is 0.. 

6. Describe the operation and characteristics of the ideal non inverting amplifier
-In this arrangement, input signal is applied in the non-inverting input terminal and ground. The inverting input is connected to the ground. The feedback resistor is connected between the output and inverting input terminals. 
-In a non-inverting amplifier, the input and output signals are same phase. The main benefit is that its gain does not depend on the active component parameter but on the passive component, so the gain of the amplifier is highly stable. According to Miller’s theorem, if the voltage gain is infinite, then this close-loop amplifier inverting input terminal acts as virtual ground, that is the potential of this point is zero with respect to the ground, but physically it is not connected to the
ground. 
-The analysis of the non-inverting amplifier is the same as for inverting amplifier
-We assume no current enter the input terminal since the input resistance is infinite.  

7. Describe the voltage follower. what are the advantages of using this circuit.

 

Ideal op amps model have infinite voltage gain, infinitely high impedance, zero output impedance, its gain is independent of input frequency, it has zero voltage offset, its output can swing positive or negative to the same voltages as the supply rails, and its output swings instantly to the correct value.The input voltage is the difference voltage between the two input terminals. The output voltage is measured with respect to the circuit ground node. The terminal characteristics of the ideal op amp satisfy four conditions which is:
-the current in each input lead is zero. 
-The output voltage is independent of the output current.
-The voltage gain A is independent of frequency. 
-The voltage gain A is very large, approaching infinity in the limit

Therefore, In a closed loop the output attempts to do whatever is necessary to make the voltage difference between the inputs zero and the inputs has no current
 

-Inverting amplifier is one in which the output is exactly 180 degree out of phase with respect to input for example  if you apply a positive voltage, output will be negative. Therefore, the output voltage changes in an opposite direction to the input voltage

- the concept of  virtual ground is that the voltage at that particular node is almost equal to ground voltage (0V). It is not physically connected to ground. This concept is very useful in analysis of op amp circuits and it will make a lot of calculations very simple. The virtual ground concept aids circuit analysis in operational amplifier and other circuits and provides useful practical circuit effects that would be difficult to achieve in other ways.

-It  means that the output voltage is independent of output current. Real, physical op-amps only approximate this ideal and have very large input impedance and very low output impedance.

A high load impedance also means there won't be much current, which also means less power. The ideal op-amp has infinite input impedance and zero output impedance because it's easy to make the input impedance lower by putting a resistor in parallel or the source impedance higher by putting a resistor in series.

Characteristic: it is used to combine the voltages present on two or more inputs into a single output voltage.

Operation: it  is used as a virtual earth mixer as it is used to combine the voltages present on two or more inputs into a single output voltage. It finds many uses where several analogue signals need to be summed. One is as an audio mixer.

- Characteristic: Non Inverting amplifier is one in which the output is in phase with respect to input.

-Operation: for example,if you apply a positive voltage, output will be positive .  Output is an Non inverted(in terms of phase) amplified version of input.

In an inverting amplifier, the output voltage changes in an opposite direction to the input voltage. The output voltage changes in an opposite direction to the input voltage. resistor is   inserted between the non-inverting input and ground, this will reduce the input offset voltage due to different voltage drops due to bias current, and may reduce distortion in the op amps.

 

Q1) Describe the ideal Op-Amp model and describe the implications of this ideal model in terms of input currents and voltages. 

 

An ideal op amp is an op amp that has perfect conditions so it can function as an op amp with 100% efficiency. Ideal op amp has infinite voltage gain, zero output impedance, the gain is independent of input frequency, infinite high impedance, it has zero voltage offset. And the implication in terms of input currents and voltages;

 

1. Gain bandwidth product is infinity 

2. Infinite voltage gain 

3. Infinite input impedance 

4. Zero output impedance 

5. Zero input offset voltage 

 

Q2) Describe the operation and characteristics of the ideal inverting amplifier. 

 

Op Amp can be in inverting amplifier circuit or non-inverting amplifier circuit. The difference between both circuits is where the op-amp connected. So, in inverting amplifier, op-amp is connected to the feedback. It inverts input to receive feedback from the output of the amplifier. Then it will produce closed loop operation. During the inverting operational amplifier, there will be no current flow in or out of the input terminal. So, when there is no current flow, the differential input will be zero. This is because at virtual earth, the input and the feedback signal is at the same potential with positive input which is at 0V. Hence, V₁ will be equal to V₂. The virtual earth then will caused the input resistance of the amplifier equal to the input value of resistor. 

 

Q3) What is the concept of virtual ground? 

 

Virtual ground is refer to the virtual one and not the real ground. But we can consider it as equivalent to the real ground with some reasons. The virtual ground means that the voltage at that particular node is almost equal to ground voltage. But it is not physically connected to ground.  Virtual ground concept is very useful in analysis of an operational amplifier when negative feedback occur. We can easily explain and make calculation. Consider an inverting op amp configuration with negative feedback. Based on the ideal op amp, the input impedance is infinity. So, no current flows through the op amp and the current flowing through V₁ will be zero. By Ohm’s Law we could conclude that Va=0, V= I x R, as I is zero and V will also be zero. 

 

 

Q4) What is the significance of a zero output resistance? 

 

The output resistance comes from internal source that has an associated with
 series resistance. The effective resistance resulted is called the output
 resistance. The negative feedback lowers output resistance, which is usually
 low enough for practical purposes that it is considered to be zero. The ideal
 op-amp has infinite input impedance and zero output impedance because it's easy
 to make the input impedance lower by putting a resistor in parallel or the
 source impedance higher by putting a resistor in series. The low resistance can
 reduce the noise and disturbance. In order to have the input current to fully
 enter the amplifier, the input resistance must decrease to ensure it flows
 easily through the input circuit. 

 

Q5) Describe the operation  and characteristics of the ideal summing amplifier 

 

Summing amplifier is another type of inverting amplifier. As indicates by its name, it enable us to add several signal together. In inverting amplifier, there is only a single voltage
 signal applied to it. However, it can be easily modified by combining the
 voltage present on several inputs in parallel so it will make a single output
 voltage. If we add more input resistor to the input, each of it will have the
 same value with the previous input resistor and will cause another summing
 amplifier circuit. In summing amplifier, the value of output voltage is the
 total of voltages input . By referring to the Ohm's Law or by applying KCL or KVL,we can find another input. 

 

Q6) Describe the operation and characteristics of the ideal non inverting amplifier 

 

In the non-inverting, the output will be the same phase as the input. Then we have a portion that go back to the inverting input. It's in the same phase. Recall that an op amp amplifies the difference. If we had the same phase of input on both inputs, then, again, this will tend to weaken the signal. This idea of negative feedback is that the feedback opposes the original input signal. Since the op amp ideally has infinite input resistance, no current flows into the input. This effectively has infinite input impedance. The input voltage will go across this resistance. 

 

Q7) Describe the voltage follower. what are the advantages of using this circuit. 

 

A voltage follower is an op amp circuit which has a voltage gain of 1. It does not provide any amplification to the signal and the output voltage directly follows the input voltage. So V₀=Vi. An op amp circuit is a circuit with very high input impedance. The advantage is that its input resistance is very large and output resistance is very small, so that it can be used as an impedance transformer or buffer circuit. The impedance transformer or buffer is used to avoid the loading effect on the circuit. This is the reason why the voltage followers are used. A voltage follower uses an op amp to set the voltage on the output to be the same as the voltage on the input. But it has limited drive capability 

 

1. Describe the ideal Op-Amp model and describe the implications of this ideal model in terms of input currents and voltages. 

- The ideal op amp is a three terminal circuit element that is modeled as a voltage-controlled voltage source. That is, its output voltage is a gain multiplied by its input voltage. An Operational Amplifier, or op-amp for short, is fundamentally a voltage amplifying device designed to be used with external feedback components such as resistors and capacitors between its output and input terminals. These feedback components determine the resulting function or “operation” of the amplifier and by virtue of the different feedback configurations whether resistive, capacitive or both, the amplifier can perform a variety of different operations, giving rise to its name of “Operational Amplifier 

2. Describe the operation and characteristics of the ideal inverting amplifier. 

- inverting amplifier: 

·Inverting amplifier is one in which the output is exactly 180 degree out of phase with respect to input(i.e. if you apply a positive voltage, output will be negative). 

· Output is an inverted(in terms of phase) amplified version of input. 

· Assuming the op-amp is ideal and applying the concept of virtual short at the input terminals of op-amp, the voltage at the inverting terminal is equal to non inverting terminal. 

 

3. What is the  concept of virtual ground? 

- a virtual ground (or virtual earth) is a node of a circuit that is maintained at a steady reference potential, without being connected directly to the reference potential. In some cases the reference potential is considered to be that of the surface of the earth, and the reference node is called "ground" or "earth" as a consequence. 

-The virtual ground concept aids circuit analysis in operational amplifier and other circuits and provides useful practical circuit effects that would be difficult to achieve in other ways. 

-In circuit theory, a node may have any value of current or voltage but physical implementations of a virtual ground will have limitations of current handling ability and a non-zero impedance which may have practical side effects. 

4. What is the significance of a zero output resistance? 

It  means that the output voltage is independent of output current. Real, physical op-amps only approximate this ideal and have very large input impedance and very low output impedance. 

A high load impedance also means there won't be much current, which also means less power. The ideal op-amp has infinite input impedance and zero output impedance because it's easy to make the input impedance lower by putting a resistor in parallel or the source impedance higher by putting a resistor in series. 

 

5. Describe the operation  and characteristics of the ideal summing amplifier 

- The Summing Amplifier is another type of operational amplifier circuit configuration that is used to combine the voltages present on two or more inputs into a single output voltage 

- Summing amplifier is a versatile device, used to combine the signals. These amplifiers add the signals directly or scale them to fit some prearranged combination rule. 

· These amplifiers are used in an audio mixer to add different signals with equal gains 

·There are various resistors are used at the input of the summing amplifier to give a weighted sum. This can be used to change a binary number to a voltage in an AC (digital to analog converter) 

·This amplifier is used to apply a DC offset voltage with an AC signal voltage. This process can be done in an LED modulation circuit to maintain the LED in its linear operating range. 

 

6. Describe the operation and characteristics of the ideal non inverting amplifier 

- The op amp non-inverting amplifier circuit provides a high input impedance along with all the advantages gained from using an operational amplifier. 

Although the basic non-inverting op amp circuit requires the same number components as its inverting counterpart, it finds uses in applications where the high input impedance is of importance.The basic circuit is relatively straightforward. 

7. Describe the voltage follower. what are the advantages of using this circuit. 

- A voltage follower is also known as a unity gain amplifier, a voltage buffer, or an isolation amplifier. In a voltage follower circuit, the output voltage is equal to the input voltage; thus, it has a gain of one (unity) and does not amplify the incoming signal. The voltage follower does not need any external components 

- the advantages is it has a very high input impedance, which means that they don’t suck in much current (ideally, none) at the inputs. Op amps also have a very low output impedance. One application where this is useful is in a voltage divider. In a voltage divider it’s possible that the impedance load (Ro) can vary quite a bit. 

1.The ideal op amp is a three terminal circuit element that is modeled as a voltage-controlled voltage source. That is, its output voltage is a gain multiplied by its input voltage. The input voltage is the difference voltage between the two input terminals. The terminal characteristics of the ideal op amp satisfy four conditions which are the current in each input lead is zero, the output voltage is independent of the output current, the voltage gain A is independent of frequency and the voltage gain A is very large, approaching infinity in the limit. The first condition implies that the resistance seen looking into both input terminals is infinite. The second implies that the voltage gain is independent of the output current. This is equivalent to the condition that the output resistance is zero. The third implies that the bandwidth is infinite. The fourth implies that the difference voltage between the two input terminals must approach zero if the output voltage is finite. 

 

 

2. In this inverting Amplifier circuit the operational amplifier is connected with feedback to produce a closed loop operation. When dealing with operational amplifiers there are two very important rules to remember about inverting amplifiers, these are: “No current flows into the input terminal” and that the differential input is zero. 

 

 

3. The circuit is a special case of an inverting amplifier where the input resistor is replaced with a short circuit. Because the v− terminal is a virtual ground, the input resistance is zero. The output resistance is also zero. Because i1 +iF = 0 and vO = iFRF . 

 

4. The ideal op-amp has infinite input impedance and zero output impedance because it's easy to make the input impedance lower (put a resistor in parallel) or the source impedance higher (put a resistor in series). It's not so easy to go the other way; you need something that can amplify. An op-amp as a voltage follower is one way to transform a high source impedance into a low source impedance. 

 

5. The Summing Amplifier is another type of operational amplifier circuit configuration that is used to combine the voltages present on two or more inputs into a single output voltage. Although, there are many ways to make a summer, this one is nice because it keeps the interaction between inputs at a minimum. Change the gain or add another input without messing with the gains of the other inputs. Just remember that the circuit also inverts the input signals.It need the opposite polarity, put an inverting stage before or after the summer. 

 

 

6. The input voltage vI is applied to the non-inverting op amp input. A voltage divider consisting of resistors RF and R1 connects from the output node to the inverting input. The circuit is called a non-inverting amplifier because its voltage gain is positive. This means that if the input voltage is increasing or going positive, the output voltage will also be increasing or going positive. If the circuit diagrams of the inverting and the non-inverting amplifiers are compared, it can be seen that the circuits are the same if vI = 0. Thus the only difference between the two circuits is the node at which the input voltage is applied. 

 

 

7. The voltage follower or unity-gain buffer is a unity-gain non-inverting amplifier. Compared to the non-inverting amplifier of the feedback resistor RF is replaced by a short circuit and resistor R1 is omitted. Because the output node is connected directly to the inverting input instead of through a voltage divider, the circuit is said to have 100% feedback. Because v+ = v−, it follows that vO = vI . Therefore, the circuit has unity voltage gain. The voltage follower is often used to isolate a low resistance load from a high output resistance source. That is, the voltage follower supplies the current to drive the load while drawing no current from the input circuit. 

 

 

3. The virtual ground means when the voltage at that particular node is almost equal to ground voltage which is 0 V but it is not actually grounded. It can be when we providing a negative feedback to the op amp.

4.  The significance of zero output resistance is that when an op amp produces its output signal, we want the op amp to have zero voltage so that the maximum voltage will be transferred to the output load. 

5. The operation of summing amplifier is to combine the voltages present on two or more inputs into a single output voltage.

6.   In non-inverting Op-Amp configuration, the input is applied at the non-inverting terminal of the op-amp and feedback is applied from the output the inverting end of the op-amp. In this configuration, the input and output voltages are in phase with each other. 

The input impedance of this configuration is ideally infinite and practically it is very high. 

7.  A voltage follower is when the output voltage is equal to the input voltage. The advantages of this circuit are the op-amp can provide current and power gain. It also providing a large input resistance and very small output resistance that can be used as a buffer circuit. 

 

1)  An ideal Operational Amplifier is a model consisting of 3 elements. It has a voltage-dependent voltage source with high gain, and modeled with 2 differential input terminals and a single output terminal. Some of its characteristics are infinite input impedance, zero output impedance, infinite voltage gain and infinite bandwidth. 

Infinite input impedance makes the input current to be zero or cannot flow through each input. The differential input voltage is also zero. 

2) An Inverting amplifier is an arrangement of op-amp when the input signal, is applied to the inverting (negative) terminal. It is called an inverting amplifier because its voltage gain is negative. For example, if the input voltage is low, the output voltage produced will be high, and vice versa. The op-amp is connected to feedback to produce a closed loop operation. The voltage of both input terminal is the same and since the input impedance is infinity, no current flow into the both input terminals and instead it will flow through the resistor. So, both input voltage is zero. 

 

Some of its characteristics are infinite input impedance, zero output impedance, and infinite open loop gain. 

 

3) Virtual ground is a term to say that the voltage at that particular node is almost equal to ground voltage which is 0 V while it is not physically connected to ground. Because of the zero voltage, it is called “virtual” ground as if it is connected to the ground. This concept is very useful in analysis of op-amp circuits and it will simplify a lot of calculation. 

4) The output resistance is the measure of the opposition to current flow. An ideal voltage source should have zero output resistance so that changes in the load such as higher load currents do not cause a voltage drop at the output, causing the output voltage to rise. The low resistance also helps in reducing the noise and interference. 

5)  Summing amplifier a type of inverting amplifier configuration. It enable us to sum up several signals together. In an inverting amplifier, there is only a single voltage signal applied to it. However, it can be easily modified by combining the voltage present on several inputs in parallel so it will make a single output voltage. If we add more input resistor to the input, each of it will have the same value with the previous input resistor and will cause another summing amplifier circuit. In a summing amplifier, the value of output voltage is the total of the input voltages that is parallel to one another. 

 

6) A Non-inverting amplifier is an arrangement of op-amp when the input signalis applied to the non-inverting terminal. The voltage gain of non-inverting amplifier is at positive input terminal. The input voltage signal is applied directly to the positive input terminal, which means that the output gain of the amplifier will become positive in value. The voltage gain is always greater than one. The result of output signal is in-phase with the input signal.  A non-inverting amplifier amplifies an input signal without inverting the signal. Meaning that, if the input signal is positive, the output signal is positive, and vice versa.  Next, the voltage at both input is the same. If the output of the circuit remains within the supply of the amplifier, then the output voltage divided by the gain which means that there is virtually no difference between the two inputs. 

7)  A voltage follower is an op-amp arrangement that is known as unity-gain amplifier or buffer amplifier which has a voltage gain of 1. The op amp acts as a buffer which does not provide any amplification to the signal. It is called a voltage follower because the output voltage directly follows the input voltage which means that the output voltage is the same as the input voltage. When a circuit has a very high input impedance, the current is dropped in the circuit. Referring to the Ohm's law, I=V/R where the greater the resistance, the less current is dropped from a power source. Thus, the power of the circuit isn't affected when current is feeding a high impedance load. It will not disturb the original circuit, and give the same voltage signal as output. It only draw very little power from the signal source, avoiding "loading" effects.   

1. Describe the ideal Op-Amp model and describe the implications of this ideal model in terms of input currents and voltages. 

 i. The output attempts to do whatever is necessary to make the voltage difference between the inputs zero. 

 ii. The input draws no current. 

2. Describe the operation and characteristics of the ideal inverting amplifier.  

3. What is the concept of virtual ground? 

4. What is the significance of a zero output resistance? 

5. Describe the operation  and characteristics of the ideal summing amplifier 

6. Describe the operation and characteristics of the ideal non inverting amplifier 

7. Describe the voltage follower. what are the advantages of using this circuit. 

1) The ideal Op-Amp model have a few characteristics which are infinite voltage gain and input impedance, zero output impedance, infinite bandwidth and zero input offset voltage. Most op amps use dual power supplies.
The implications of this ideal model in terms of input currents and voltages is The output attempts to do whatever is necessary to make the voltage difference between the inputs zero and the input draw no current.
 2)  The input signal is applied through resistor to the inverting op amp input. The feedback resistor which connects from the output to the inverting input. If the input voltage is increasing or going positive, the output voltage will be decreasing or going negative because the voltage gain is negative. 
3)  Making a node or a connection virtually ground and its not physically connected to Ground but voltage at that point/node is zero so we refer to it as Ground.
4) An ideal constant voltage power supply should have zero output impedance so that changes in the load such as higher load currents do not cause a voltage drop at the output.
5) Combining the voltages present on two or more inputs into a single output voltage. the output voltage now becomes proportional to the sum of the input voltages. 
The summing point is connected to the inverting input of the op-amp. The circuit will produce the negative sum of any number of input voltages.
6)  The input voltage is applied to the non-inverting op amp input. A voltage divider consisting of resistors RF and R connects from the output node to the inverting input. The circuit is called a non-inverting amplifier because its voltage gain is positive. This means that if the input voltage is increasing or going positive, the output voltage will also be increasing or going positive 
7) A unity-gain non-inverting amplifier. Compared to the non-inverting amplifier ,the feedback resistor RF is replaced by a short circuit and resistor R is omitted. Because the output node is connected directly to the inverting input instead of through a voltage divider, the circuit is said to have 100% feedback. Therefore, the circuit has unity voltage gain. The voltage follower is often used to isolate a low resistance load from a high output resistance source. That is, the voltage follower supplies the current to drive the load while drawing no current from the input circuit 

An ideal op amp will have infinite voltage gain and infinitely high input impedance. It also will have zero output impedance. In an ideal op amp, the gain that the op amp produces will be independent of frequency. If no voltage is applied to the inverting and non inverting input pins, the op amp will output a voltage of 0, since there is no difference at all of the voltage applied to the 2 input pins.

2. Describe the operation and characteristics of the ideal inverting amplifier.

The input signal is applied through resistor R1 to the inverting op amp input. Resistor RF is the feedback resistor which connects from the output to the inverting input. The circuit is called an inverting amplifier because its voltage gain is negative. If the input voltage is increasing or going positive, the output voltage will be decreasing or going negative, and vice versa.

3. What is the concept of virtual ground?

Virtual ground means that the voltage at that particular node is almost equal to ground voltage. It is not physically connected to ground. The voltage is approximately zero and not able to sink infinite current. 

4. What is the significance of a zero output resistance?

The significance of zero output resistance is means it can supply as much current as necessary to the load. The output resistance of the ideal operational amplifier is assumed to be zero. So, it supply maximum current to the load.

5. Describe the operation and characteristics of the ideal summing amplifier

Ideal summing amplifier is used to add two signal voltages. The circuit of the voltage adder is so simple to construct and it enables to add many signals together. This kind of amplifiers is used in a wide range of electronic circuits. For summing amplifier, it is possible to apply more than one input single to an inverting amplifier. This circuit will then add all this input signals to produce at the input. The input resistance is infinity and the input current is 0. 

6. Describe the operation and characteristics of the ideal non inverting amplifier

In the non-inverting circuit, the input impedance Rin has increased to infinity and the feedback impedance Rƒ reduced to zero. The output is connected directly back to the negative inverting input so the feedback is 100% and Vin is exactly equal to Vout giving it a fixed gain of 1 or unity.

 the input impedance is infinite (ideal op-amp) and also no current flows through the feedback loop so any value of resistance may be placed in the feedback loop without affecting the characteristics of the circuit as no voltage is dissipated across it, zero current flows, zero voltage drop, zero power loss.

7. Describe the voltage follower. what are the advantages of using this circuit.

A voltage follower is a op-amp circuit which has a voltage gain of 1.The op amp does not provide any amplification to the signal. The output voltage directly follows the input voltage, meaning the output voltage is the same as the input voltage. Voltage follower has three unique characteristics which are extremely high input impedance, extremely low output impedance and unity transmission gain. Therefore, an ideal circuit device for use as a buffer amplifier.

 

1.       Ideal Op Amp is when the input impedance (input resistance) is infinity and the output impedance (output resistance) equal to zero. Its implication to the input current and voltage, they will be block by this input impedance which is infinity.

 

2.       Input resistance is infinite.

Output resistance is zero.

Differential input voltage equal to zero.

Internal differential gain is infinite.

No current flow.

V1 – V2 = 0, V1=V2

So that it will give out maximum output voltage or current with such minimum input voltage or current.

 

3.       In Ideal Op Amp, the input resistance is infinite, so the virtual ground is a concept for calculation purposes and analyzing because the initial current is zero due to the infinite resistance. So, that we know where the current goes and easier to analyze.

 

4.       The significance is so that the amplifier will be efficient which it will give the maximum output voltage.

 

5.       Different source can be sum to a single source because of all of it will connect to one of the terminal of amplifier.

 

6.       Non Inverting Amplifier is when the voltage source is connected to the positive (non-inverting) terminal of the amplifier and no voltage source connected to the negative (inverting) terminal of the amplifier. Resistor from inverting terminal form a simple potential divider network across the non-inverting amplifier with the voltage gain of the circuit being determined by the ratios of those resistor.

 

7.       Voltage follower is when the gain is equal to 1; Vo = Vi. The advantage of the voltage follower is that it can be used to maintains the signal voltage. It provide the same voltage at the output  and the voltage at the input.