IN THE EARLY YEARS OF ELECTRONICS, MOST DIODES WERE VACUUM TUBES. TODAY, MOST DIODES are made from semiconductor materials. Contemporary diodes can do almost everything that the old vacuum-tube ones could, and a few things that people in the tube era never imagined.
A rectifier diode passes current in only one direction, as long as we don’t exceed its specifications. This property makes the device useful for changing AC to DC. Generally speaking:
• When the cathode has a more negative charge than the anode, current flows.
• When the cathode has a more positive charge than the anode, current does not flow.
The constraints on this behavior are, as we’ve learned, the forward breakover and avalanche ...