Semiconductor diode amplifiers and pulse modulators

The reverse recovery characteristic of a semiconductor diode depends not only on the crystal properties and the physical dimensions of the diode but also on the circuit in which it is used. The effects of the circuit parameters, namely, forward current, reverse voltage and reverse loop impedance, on the diode recovery characteristics were studied experimentally on germanium and silicon junction diodes. The results are given in curves which illustrate the relationships between these circuit parameters and the maximum reverse current, as well as the constant current duration. Based on these curves, circuit applications were developed. The experiments on a pulse amplifier performed by the National Bureau of Standards, were repeated. The results showed a maximum power gain of 22 db per stage. Four pulse modulator circuits were designed. They are amplitude modulator, sampler, pulse duration and position modulators. Linearity and frequency response tests on these modulator circuits were conducted. The results indicated that they have small distortion and flat frequency response from dc up to several tens of kilocycles per second. Modifications of the pulse amplitude modulator provides amplifiers for continuously varying signals. Four such circuits are given.