EC-6.4 Diodes in Circuits: Rectifiers, Clippers, Clampers and the Zener

Work through these

• Three diode models, and choosing the crudest one that answers the question

  A diode can be treated as an ideal switch, as a switch with a fixed voltage drop, or as a drop with a series resistance. Reaching for the exponential when a switch would do is the commonest way to make a short problem long.

  MIT OpenCourseWare 6.012: Microelectronic Devices and Circuits · Course

• Assume, solve, check: the method for any circuit with diodes

  Guess which diodes conduct, replace each with its model, solve the linear circuit, then verify every conducting diode has forward current and every off one has reverse voltage. An inconsistent result means the guess was wrong, not the arithmetic.

• Half-wave and full-wave rectifiers, and what the bridge buys

  One diode passes half the input and a bridge of four passes both halves with the negative one inverted, doubling the average output. The bridge costs two diode drops instead of one, which matters at low voltages.

  NPTEL: Introduction to Semiconductor Devices · Course

• Smoothing, and sizing a capacitor from the ripple you will tolerate

  A capacitor across the output holds the voltage up between peaks, discharging into the load in the gaps. Ripple follows from the load current, the capacitance and the time between peaks, which is enough to choose a value.

• Clippers and clampers, and the difference between them

  A clipper removes part of a waveform by conducting once a threshold is passed, while a clamper adds a constant offset by charging a capacitor to it. One changes the shape and the other moves it.

• The Zener diode, and using reverse breakdown deliberately

  Driven far enough in reverse a junction breaks down at a well-controlled voltage and holds it while current varies widely, which makes a simple reference. It is only destructive if the current is not limited by something else.

  NPTEL: Solid State Devices · Course