LD502

The LD502 is a compression (AGC) preamplifier that consists of a single ended input inverting amplifier, with an internal current controlled resistance connected between input and output.

By using RGT (see test circuit) to vary the value of this current controlled resistance, the amplifier gain and compression threshold can be controlled over a range of 60 dB.

The AGC current LD502 is derived from a full wave rectifier driven by a differential amplifier. The attack time of the AGC circuit is fixed at less than 1 ms. The release time is adjustable from 40 to 500 ms by selecting the value of an external capacitor (C3).

Internally, a series shunt voltage regulator produces a 0.94 V DC regulated output voltage. This provides a bias for electret microphones and permits circuit operations over a wide range of supply voltages, 1.05 to 3 VDC for LD502 without any degradation of electrical performances.