Op Amp Circuits: A Comprehensive Guide

Operational amplifiers, or op-amps, are versatile electronic devices that have found their way into countless applications across various fields. Whether you’re a hobbyist, an engineer, or a student, understanding op-amp circuits is crucial. In this detailed guide, we’ll explore the basics, different types of op-amp circuits, and their applications.

Understanding Op-Amps

Before diving into specific circuits, it’s essential to have a solid understanding of what an op-amp is. An op-amp is an electronic voltage amplifier with differential inputs and, typically, a single output. It amplifies the difference between the two input voltages and produces an output voltage that is typically much larger than the input voltages.

Op-amps are often represented by a symbol that consists of a triangle with two inputs and one output. The triangle represents the amplifier, while the inputs and output represent the voltage points where signals are applied and taken from.

Basic Op-Amp Circuit: Inverting Amplifier

The inverting amplifier is one of the most fundamental op-amp circuits. It provides an inverted output signal with a gain determined by the ratio of the feedback resistor to the input resistor. The circuit consists of an op-amp, an input resistor (R_in), and a feedback resistor (R_fb).

Here’s how it works: The input signal is applied to the inverting input (-) of the op-amp, and the output is taken from the output terminal. The non-inverting input (+) is connected to ground. The voltage gain (A) of the inverting amplifier is given by the formula A = -R_fb/R_in.

Non-Inverting Amplifier

The non-inverting amplifier is another popular op-amp circuit. Unlike the inverting amplifier, the non-inverting amplifier provides an amplified output signal that is in phase with the input signal. The circuit consists of an op-amp, an input resistor (R_in), and a feedback resistor (R_fb).

In this circuit, the input signal is applied to the non-inverting input (+) of the op-amp, and the output is taken from the output terminal. The non-inverting input (-) is connected to ground. The voltage gain (A) of the non-inverting amplifier is given by the formula A = 1 + R_fb/R_in.

Op-Amp as a Summing Amplifier

The summing amplifier is a versatile op-amp circuit that can combine multiple input signals into a single output signal. The circuit consists of an op-amp, input resistors (R₁, R₂, …, R_n), and a feedback resistor (R_fb).

In this circuit, each input signal is applied to a separate input resistor, and the output is taken from the output terminal. The voltage gain (A) of the summing amplifier is given by the formula A = -R_fb/R₁.

Op-Amp as a Differential Amplifier

The differential amplifier is an op-amp circuit that amplifies the difference between two input signals while rejecting any common-mode signals. The circuit consists of two op-amps, input resistors (R₁, R₂), and a feedback resistor (R_fb).

In this circuit, each input signal is applied to a separate input resistor, and the output is taken from the output terminal. The voltage gain (A) of the differential amplifier is given by the formula A = -R_fb/R₁.

Op-Amp as a Schmitt Trigger

The Schmitt trigger is an op-amp circuit that provides hysteresis, which makes it useful for noise reduction and signal shaping. The circuit consists of an op-amp, resistors (R₁, R₂), and a diode.

In this circuit, the input signal is applied to the inverting input (-) of the op-amp, and the output is taken from the output terminal. The non-inverting input (+) is connected to ground. The voltage gain (A) of the Schmitt trigger is given by the