Question

In which of the following applications is the operational amplifier used in **nonlinear mode**?

• A. Integrators
• B. Active filters
• C. Schmitt triggers
• D. Instrumentation amplifiers

Hint:

Op-amp is in nonlinear mode in Schmitt triggers (hysteresis), comparators, etc.

Answer 1

The Correct Option is C

An operational amplifier, commonly referred to as an op-amp, can be used in both linear and nonlinear applications. The distinction lies in how the op-amp is configured within the circuit:

• Linear Mode: In linear applications, the output signal maintains a linear relationship with the input. Common linear applications include integrators, active filters, and instrumentation amplifiers.
• Nonlinear Mode: In nonlinear applications, the op-amp generates output not directly proportional to the input, often used for signal threshold detection or waveform shaping.

Let's analyze the given options:

Integrators: Used for mathematical integration of input signals, these circuits take an input current and produce an output voltage that approximates the integral of the current over time. Integrators are classified as linear applications.

Active Filters: These circuits modify signal frequencies, amplifying or attenuating them based on their frequency. Active filters maintain linearity in signal processing.

Schmitt Triggers: These are used to convert an analog input signal to a digital output signal, characterized by hysteresis, a property ensuring stability even with noisy inputs. The Schmitt trigger operation is inherently nonlinear because it involves thresholding, a nonlinear operation.

Instrumentation Amplifiers: Designed to amplify small differential signals while rejecting large common-mode voltages, they function in a linear manner, emphasizing precision and accuracy.

Given these explanations, only the Schmitt triggers utilize the operational amplifier in a nonlinear mode. This is primarily because of their unique ability to cleanly convert a noisy input signal into a square wave output using threshold levels.