Voltage comparator circuit diagram

Voltage comparator circuit .

A voltage comparator compares two voltages and switches the output to either a high or low state, depending on the circuit with the higher voltage. An op amp based voltage comparator is displayed. Figure 1 shows the inverting mode of a voltage comparator. The diagram shows the voltage comparison in non-inverting mode.

voltage comparator

Non-inverting comparison

The reference voltage in the non-inverting comparator is applied to the inverting input voltage for comparison to the non-inverting input. Whenever the voltage being compared (Vin) is above the reference voltage the op amp's output swings into positive saturation (V+), and vice versa. What actually happens is that the difference between VIN and Vref (VIN - VREF), will be a positive value and amplified by the op amp to infinity. Since there is no feedback resistor Rf, the op amp is in open loop mode, so the voltage gain (AV) will be close to infinity. +So the largest possible value, which is the output voltage swing, V. Remember the formula AV = 1 +(Rf/R1). When VIN is lower than VREF, reverse direction occurs.

inverse comparison

In the case of phase comparison, a reference voltage is applied to the non-inverting input and the voltage to be compared is applied to the inverting input. Whenever the input voltage (Vin) is higher than VREF, the op amp's output swing negatively saturates. Here, the sum of the differences between the two voltages (VIN-VREF) is amplified to infinity by the op amp. Remember the formula AV = -Rf/R1. The voltage gain in inverting mode is calculated as AV = -Rf/R1.Since there is no feedback resistor, the gain will be close to infinity and the output voltage will be as negative as possible, V-.

Actual voltage comparator circuit

A practical inverting comparator that is not based on the UA741 op amp is shown below. Here a voltage divider network consisting of R1 and R2 is used to set the reference voltage. The equation is VREF = (V + / (R1 + R2)) × R2. Substituting the circuit diagram values ​​into this equation, VREF = 6V. When VIN is higher than 6V, the output swings to +12V DC and vice versa. Circuit powered from A+/- 12V DC dual supplies.

Use of voltage comparators 741

Some other op amps and related circuits you might be interested in

1 Summing amplifier: Summing amplifiers can be used to find the algebraic sum of a given number of signals.

2. Integrated using op amps: For an integrated circuit, the output signal will be the integral of the input signal. For example, integrating a sine wave into a cosine wave, integrating a square wave into a triangle wave, etc.

3. Inverting Amplifier: In an inverting amplifier, the output signal will be an inverted version of the input signal, which is amplified by some factor.

4. Instrumentation Amplifier: This is a type of differential amplifier with an additional buffering stage on the input. High input impedance makes matching results easy. Instrumentation amplifiers have better stability, high common-mode rejection ratio (CMRR), low offset voltage, and high gain.