Pulsed feedback circuit for opto-electronic detector - forms optically coupled current amplifier with input impedance low in forward direction and high in reverse direction

摘要

An LED (DI) is driven by a current amplifier (T2) which is controlled by a phototransistor (T1) via a current amplifier input and a filter (R1, C1). The current amplifier input has low impedance in the forward direction and high impedance in the reverse direction. Rising current transients in a load (R3) are selectively amplified by optical coupling (D1, T1), so that the LED emits sharp pulses separated by completely dark spaces. The amplitude and frequency of the pulses depend on the feedback factor.