**Op Amps with Negative Feedback Interview Questions and Answers:**

**1. What kind of negative feedback is present in a noninverting op-amp?**

**Ans.** Negative voltage series feedback.

**2. What is effect of negative feedback in a noninverting amplifier on input impedance and bandwidth?**

**Ans.** Negative feedback in a noninverting amplifier increases each of the input impedance and bandwidth by a factor (1 + AB) where AB is feedback factor.

**3. What is a voltage follower?**

**Ans.** Voltage follower is an electronic circuit in which output voltage tracks the input voltage both in sign and magnitude.

**4. What are the advantages of using a voltage follower amplifier?**

**Ans.** Voltage follower has three unique characteristics viz extremely high input impedance, extremely low output impedance and unity transmission gain and is, therefore, an ideal circuit device for use as a buffer amplifier.

**5. In what way is the voltage follower a special case of the non-inverting amplifier?**

**Ans.** If feedback resistor is made zero or R_{1} is made ∞ (by keeping it open circuited) in a noninverting amplifier circuit, voltage follower is obtained.

**6. What is an inverting amplifier?**

**Ans.** In an inverting amplifier, the input is connected to the minus or inverting terminal of op-amp.

**7. How does negative feedback affect the performance of an inverting amplifier?**

**Ans.** Negative feedback decreases the voltage gain, nonlinear distortion, noise, output impedance and total output offset voltage and increases the input impedance and bandwidth.

**8. What are the applications of an inverting amplifier?**

**Ans.** Inverting amplifier is a very versatile component and can be used for performing number of mathematical stimulation such as analog inverter, paraphrase amplifier, phase shifter, adder, integrator, differentiator.

**9. What is a differential amplifier?**

**Ans.** Differential amplifier is a combination of inverting and noninverting amplifiers and amplifies the voltage difference between two input lines neither of which is grounded.

**10. Are the characteristics of dual op-amp differential amplifier similar to those of inverting amplifier?**

**Ans.** No. The characteristics of a dual op-amp differential amplifier are identical to those of a noninverting amplifier.

**11. What is the drawback of dual op-amp differential amplifier?**

**Ans.** The possible reduction in the amplitude of the output signal is the drawback of dual op-amp differential amplifier.

**12. What is the effect on input resistance if two op-amps are used as differential amplifier?**

**Ans.** Input Resistance. Input resistance of first stage, R_{inf2} = R_{in} (1 + AB)

where R_{in} is the open-loop resistance of op-amp, as first stage is noninverting amplifier.

With v_{in2} grounded i.e. v_{in2} = 0, the second stage also becomes a noninverting amplifier whose input resistance may be given as

where R_{in} is open-loop resistance of op-amp