Constant Volume FET Amplifier Circuit

In numerous occasions it is desirable to obtain an amplifier that gives an output signal of constant amplitude for numerous input signal levels and with the very least distortion.

A traditional way out of this challenge is to use a nonlinear amplifier.

An operational, as an illustration, run as a nonlinear amplifier if 2 antiparallel diodes are included in the feedback loop.

This program, nevertheless, while offering an output signal of close to constant amplitude, carries a setback: severe distortion.

How it Works

A more exquisite solution is to apply a constant volume FET amplifier circuit as shown in Fig below.

In such cases, the nonlinear ingredient is restored with the FET (Q1) and its associated elements.

When a small operational signal (741) is applied, its output is smaller.

As a result, the gate of the FET receives an incredibly minimal negative bias and the resistance between drain and source is substantial. As a result, the voltage gain is high.

The opposite happens in the event the input signal is bigger. Consequently, the common measure of the output signal self-regulates between 1.5V and 2.85V over a range of 50: 1 difference in the degree of the input signal without producing audible distortion.

The value of R1 is determined by the optimum expected amplitude of input signal and is established on a per 200k volt RMS. As an illustration, to satisfy up to 50Vrms signals R1 must 10M.

Circuit of a constant volume FET amplifier