Op AMP Voltage Comparator – theteche.com

If both inputs of the op amp shown in Fig. 1 are used simultaneously, then from equation, the output voltage is given by:

Vo = Ao(V2 − V1)

Op AMP Voltage

When V2 > V1 then Vo is positive, its maximum value being the positive supply voltage + Vs, which it has when (V2 > V1) ≥ Vs/Ao. The op amp is then saturated. For example, if Vs = +9 V and Ao = 105, then saturation occurs when

\left(V_2-V_1\right) \geq \frac{9}{10^5}

i.e. when V2 exceeds V1 by 90 μV and Vo ≈ 9 V. When V1 > V2, then Vo is negative and saturation occurs if V1 exceeds V2 by Vs/Ao i.e. around 90 μV in the above example; in this case, Vo ≈ −Vs = −9 V.

Op AMP Voltage Comparator

A small change in (V2 − V1) therefore causes Vo to switch between near +Vs and near to −Vs and enables the op amp to indicate when V2 is greater or less than V1, i.e. to act as a differential amplifier and compare two voltages. It does this in an electronic digital voltmeter.

Read More Topics
Introduction to operational amplifiers
Maximum power transfer theorem
Conduction in semiconductor materials
Introduction to electromagnetic induction

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