# Operational amplifier multivibrator oscillator circuit

### - circuit, equations and design details for a simple multivibrator oscillator using a single op amp or operational amplifier.

Op-amp circuits include:

• Operational amplifier circuits

• Inverting op-amp

• Non-inverting op-amp

• Op-amp high pass filter

• Op-amp low pass filter

• Op-amp bandpass filter

• Op-amp variable gain amplifier

• Op-amp notch filter circuits

• Operational amplifier multivibrator

• Op-amp bistable

• Op-amp comparator

• Op-amp Schmitt trigger

• Op-amp integrator

• Op-amp differentiator

Multivibrator oscillators are used in many electronics circuits and they are simple to construct. It is possible to construct them using a couple of transistors, but it is also possible to construct a very simple multivibrator oscillator circuit using an operational amplifier. The circuit can be used in a variety of applications where a simple square wave oscillator circuit is required.

The use of an operational amplifier integrated circuit is ideal from many viewpoints. Although circuits can be made using just two transistors, operational amplifiers are also very cheap these days, and there is often little to choose in terms of cost.

## Op amp multivibrator circuit

The operational amplifier multivibrator circuit comprises two sections. The feedback to the capacitor is provided by the resistor R1, whereas hysterisis is provided by the two resistors R2 and R3.

**Operational amplifier multivibrator oscillator**

The time period for the oscillation is provided by the formula:

**T = 2 C R1 loge (1 + 2 R2 / R3)**

Although many multivibrator circuits may be provided using simple logic gates, this operational amplifier multivibrator circuit has the advantage that it can be used to provide an oscillator that will generate a much higher output than that which could come from a logic circuit running from a 5 volt supply. In addition to this the multivibrator oscillator circuit is very simple, requiring just one operational amplifier, op amp, three resistors, and a single capacitor.

* By Ian Poole*

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