Operational Amplifiers Questions and Answers for Viva

Answer-1: An operational amplifier is a high-gain electronic voltage amplifier with two inputs (inverting and non-inverting) and a single output.

Answer-2: Ideal op-amp characteristics include infinite open-loop gain, infinite input impedance, zero input bias current, zero output impedance, and infinite bandwidth.

Answer-3: The two main input terminals are the inverting (-) and non-inverting (+) inputs. The inverting input produces an output that is 180 degrees out of phase with the input signal, while the non-inverting input produces an output in-phase with the input signal.

Answer-4: Negative feedback involves feeding back a portion of the output signal to the inverting or non-inverting input of the op-amp to stabilize and control its operation.

Answer-5: In an inverting amplifier, the input signal is applied to the inverting input terminal, and the output is 180 degrees out of phase with the input signal. The gain of the amplifier is determined by the ratio of the feedback resistor to the input resistor.

Answer-6: The gain (Av) of an inverting amplifier is given by the formula: A_v = -R_f / R_in, where R_f is the feedback resistor and R_in is the input resistor.

Answer-7: The gain (A_v) of a non-inverting amplifier is given by the formula: A_v = 1 + (R_f / R_in), where R_f is the feedback resistor and Rin is the input resistor.

Answer-8: A voltage follower, or buffer, circuit using an op-amp provides unity gain and high input impedance, allowing it to isolate the input signal from the load and provide a high-current output without affecting the input signal.

Answer-9: An integrator circuit using an op-amp integrates the input voltage signal over time to produce an output voltage proportional to the integral of the input signal. It utilizes a capacitor in the feedback loop to achieve integration.

Answer-10: A differential amplifier amplifies the voltage difference between two input signals while rejecting any common-mode signals. It typically consists of two inputs and one output.

Answer-11: An op-amp comparator compares the voltages at its two input terminals and produces a high or low output voltage depending on which input is higher. It is commonly used in applications where precise voltage comparison is required.

Answer-12: CMRR measures the ability of an op-amp to reject common-mode signals present at its input terminals. A higher CMRR indicates better rejection of common-mode noise and interference.

Answer-13: An active filter uses op-amps and other active components to filter signals, such as low-pass, high-pass, band-pass, or band-stop filters. It provides adjustable gain and higher performance compared to passive filters.

Answer-14: Temperature changes can affect the parameters of op-amps, such as offset voltage, bias current, and gain. Temperature-stable op-amps are designed to minimize these effects.

Answer-15: A summing amplifier adds multiple input signals with different gains to produce a single output voltage. It utilizes multiple input resistors and an inverting or non-inverting configuration.

Answer-16: Offset voltage is the voltage required to nullify the input voltage difference between the inverting and non-inverting input terminals of an op-amp. It can cause errors in precision applications and needs to be minimized for accurate performance.

Answer-17: Negative feedback increases the input impedance of an op-amp circuit, making it less sensitive to changes in the input signal source impedance.

Answer-18: Slew rate refers to the maximum rate of change of the output voltage of an op-amp and is typically measured in volts per microsecond (V/_μs). It limits the maximum frequency of the input signal that the op-amp can accurately amplify.