Diodes etc.

Signal Diodes

These three small glass-encapsulated "signal" diodes are used for low-current switching, as signal rectifiers and in "detector" circuits. The larger diode is a germanium type (OA91) whilst the two smaller types are silicon (1N914 and 1N4148).

Power Diodes

This power diode is designed for use as a rectifier in low and medium-voltage power supplies. The diode is rated at 200V 3A maximum and it can be bolted to a metal "heatsink" in order to dissipate heat.

Zener Diodes

This selection of zener diodes provide zener voltages of between 2.7V and 10V and maximum power dissipation of between 300mW and 1W. They are used in regulated power supplies which provide a reasonably constant output voltage regardless of variations in load current or supply voltage.

Thyristor

This thyristor or "silicon controlled rectifier" is used as a switching device in power control circuits. Thyristors are able to switch very large current at high voltage from a very small current, low voltage source. The thyristor shown here is able to switch 800V at 1A from a 20mA pulse of current at a mere 2.5V applied to its gate trigger terminal.

Triac

Like thyristors, triacs are switching devices that are used in a.c. power control applications. The difference between the two types of component is that the triac can conduct current in both directions (i.e. on positive and negative half-cycles of an a.c. waveform) whilst thyristors can only conduct in one direction. The triac shown here is supplied in a TO220 package and it is rated at 600V 1A.

Bridge Rectifier

Bridge rectifiers contain four individual power diodes connected in a bridge configuration. The complete assembly is then used as a full-wave rectifier in a power supply. The bridge rectifier shown here is designed for printed circuit mounting and it is rated at 200V 1A.

Light Emitting Diodes

Light emitting diodes (LED's) are used as indicators in a wide variety of circuits and are available in a variety of colours, including red, green and yellow. A typical LED requires a current of between 10mA and 20mA and has a forward voltage drop of about 2.3V.