Rectifier diode definition – diode designed for rectifying alternating current (mostly with low power frequency – 50 Hz at high power emitted during load). Silicon diodes are mainly used, they have large junction surface. The possibility of conducting high value of current can be classified as its basic feature. Germanium diodes have much lower permissible reversed voltage and a smaller permissible junction temperature (Tj = 75 ° C for germanium diodes and Tj = 150 ° C for silicon diode). The only advantage that germanium diode has over silicon one is lower voltage value during working in a forward-bias (VF (IO) = 0.3 ÷ 0.5V for germanium and 0.7 ÷ 1.4V for silicon).
Rectifier diode constructien are produced for working on current values from several mA to few kA and voltages up to few kV. Variant of rectifier diode with Schottky barrier (VF = 0.5 ÷ 0.6 is the advantage, whereas the downside is small voltage in the reverse bias) is particularly valued in digital electronics where switching speed of the diode plays a significant role.
We distinguish two groups of technical parameters of the rectifier diode (as well as other diodes):
- permissible limit parameters,
- characteristic parameters.
Rectifier diode is characterized by following permissible limit parameters:
- IFN – rated current in the forward bias (also known as a maximum average current of the IO diode),
- IFRM – peak, repeatable current diode conduction (for example, for the pulses with duration of no more than 3.5 ms and a frequency of 50 Hz),
- IFSM – peak, non-repeatable current conduction (eg. for a single pulse with a duration of less than 10 ms),
- VRWM – peak, reverse voltage operation (or average, reverse voltage during diode operation in wave rectifier with resistive load),
- VRRM – peak, repetitive reverse voltage,
- VRSM – peak, non-repeatable reverse voltage,
- PTOT – the maximum value of the power dissipated on the item,
- maximum Tj junction temperature,
- thermal resistance under Rth operating conditions,
- maximum instantaneous current of the diode (it determines resistance for overloads)
Characteristic parameters of rectifier diode:
- VF forward voltage with determined IF forward current (usually with a maximum average IO rectified current, also known as rated current IFN),
- IR reverse current at VRWM peak reverse voltage work.
Two examples of rectifier diode circuits: