Which among the following is the most widely used constant-gain amplifier circuit?

Amplifier:

An amplifier is a device that is used to amplify or increase the strength of the input signal. The output of the amplifier is 'k' times of the input signal.

 V_out = k × Vin 

 where ; k = DC gain

Vout is the output voltage and Vin is the input voltage

Explanation:

1) Inverting Amplifier: This amplifier produces linear output with respect to the input. It produces an output that is 180 degrees out of phase with the input.

Vout = \({-Rf \over Rin}\)  ×  Vin  

 where R_f is the feedback element and R_in is an input element

Linear property is useful for converting a small input signal to a larger output voltage, hence inverting amplifier is the most widely used constant gain amplifier circuit.

2) Subtracting Amplifier: This amplifier produces an output that is proportional to the difference between the two applied input voltages. 

 Vout = k ×  (V₁ - V₂) 

3) Non-Inverting Amplifier: This amplifier produces non-linear output with respect to the input. It produces an output that is in phase with the input.

Vout = \((1+\frac{Rf}{Rin})\)\(×\) Vin 

4) Summing Amplifier: This amplifier produces output that is proportional to the sum of two or more applied input voltages.

Vout = k \(×\)(V₁ + V₂ + .......V_n)