Schottky diode

A Schottky diodes are made of metal and semiconductor. Silicon is used as a semiconductor, and molybdenum or aluminum may be used as metal.

In this diodes there is no injection of minority charge carriers, and therefore, there is no accumulation of them in a base. This feature increases the fast-response of metal-semiconductor pulsed diodes considerably. So, they have switching time equal to a fraction of a nanosecond, and their cutoff frequency is dozens of giga-Hz.

Pulsed diodes

Semiconductor diodes are widely used as gates or switches, which are operated in two modes – “switch on” and “switch off”. This enables to switch informative signals in pulse and digital systems. Diode-resistor and diode-transistor logics consist mostly of pulsed diodes. The construction and current-voltage characteristic of pulsed diodes are the same as in high-frequency diodes. They have minimal transient process time at the moments of “switching on” and “switching off”.

There are some modes of diode operation with current and voltage oscillators. They depend on the ratio of a diode resistance to oscillator resistance.

If R_osc>>R_d, the source of informative signals is a current oscillator. In this case, the waveform of the current flowing through a diode corresponds exactly to the current waveform of the oscillator, and the waveform of the voltage drop across a diode is studied.

If R_osc<<R_d, the switched circuit is under control of the voltage oscillator, and the waveform of the current pulse flowing through a diode is studied.

Thus, it is necessary to emphasize four conditions of diode operation:

1) with current oscillator under the high-amplitude condition;

2) with voltage oscillator under the high-amplitude condition;

3) with current oscillator under the low-amplitude condition;

4) with voltage oscillator under the low-amplitude condition.