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# Waveform Generators

A **waveform generator** is an electronic circuit, which generates a standard wave. There are two types of op-amp based waveform generators −

- Square wave generator
- Triangular wave generator

This chapter discusses each of these op-amp based waveform generators in detail.

## Square Wave Generator

A **square wave generator** is an electronic circuit which generates square wave. This section discusses about op-amp based square wave generators.

The **circuit diagram** of a op-amp based square wave generator is shown in the following figure

Observe that in the circuit diagram shown above, the resistor $R_{1}$ is connected between the inverting input terminal of the op-amp and its output of op-amp. So, the resistor $R_{1}$ is used in the **negative feedback**. Similarly, the resistor $R_{2}$ is connected between the noninverting input terminal of the op-amp and its output. So, the resistor $R_{2}$ is used in the **positive feedback** path.

A capacitor C is connected between the inverting input terminal of the op-amp and ground. So, the **voltage across capacitor C** will be the input voltage at this inverting terminal of op-amp. Similarly, a resistor $R_{3}$ is connected between the non-inverting input terminal of the op-amp and ground. So, the **voltage across resistor $R_{3}$** will be the input voltage at this non-inverting terminal of the op-amp.

The **operation** of a square wave generator is explained below −

Assume, there is

**no charge**stored in the capacitor initially. Then, the voltage present at the inverting terminal of the op-amp is zero volts. But, there is some offset voltage at non-inverting terminal of op-amp. Due to this, the value present at the output of above circuit will be $+V_{sat}$.Now, the capacitor C starts

**charging**through a resistor $R_{1}$. The value present at the output of the above circuit will change to $-V_{sat}$, when the voltage across the capacitor C reaches just greater than the voltage (positive value) across resistor $R_{3}$.The capacitor C starts

**discharging**through a resistor $R_{1}$, when the output of above circuit is $-V_{sat}$. The value present at the output of above circuit will change to $+V_{sat}$,when the voltage across capacitor C reaches just less than (more negative) the voltage (negative value) across resistor $R_{3}$.

Thus, the circuit shown in the above diagram will produce a **square wave** at the output as shown in the following figure −

From the above figure we can observe that the output of square wave generator will have one of the two values: $+V_{sat}$ and $-V_{sat}$. So, the output remains at one value for some duration and then transitions to another value and remains there for some duration. In this way, it continues.

## Triangular Wave Generator

A triangular wave generator is an electronic circuit, which generates a triangular wave. The **block diagram** of a triangular wave generator is shown in the following figure −

The block diagram of a triangular wave generator contains mainly two blocks: a square wave generator and an integrator. These two blocks are **cascaded**. That means, the output of square wave generator is applied as an input of integrator. Note that the integration of a square wave is nothing but a triangular wave.

The **circuit diagram** of an op-amp based triangular wave generator is shown in the following figure −

We have already seen the circuit diagrams of a square wave generator and an integrator. Observe that we got the above **circuit diagram** of an op-amp based triangular wave generator by replacing the blocks with the respective circuit diagrams in the block diagram of a triangular wave generator.