Hi, I read many sources of how diodes are used to rectify an AC Voltage and not read anything about diodes in a DC circuit. I have seen a few DC circuits with diodes in them but I dont know why they are used. Can anyone tell me why they are used in DC circuits?

 

There are many other applications for diodes besides rectifying AC.

• 0.7V drop or reference
• transistor bias circuit
• signal limiter or clamp
• signal clipper or guitar fuzz circuit
• reverse voltage circuit protection
• back emf suppressor
• log or antilog amplifier
• peak detect circuit
• noise generator
• noise filter circuit
• RF tuning diode
• AM detector
• logic AND/OR gates
• power source automatic switch-over (submitted by JMac)
• Power-ON reset

 

A simple example is a diode OR. See the attached file for an example.

A diode OR is used when you have two voltage sources and you want the higher one to power your circuit.

In the example shown in the attached file, the diode OR output is used to power a 2-cell LiIon battery charger. The inputs to the diode OR come from two sources:

(1) 5V from USB boosted to 10V using a boost converter.
(2) 12V from an external power supply.

If only USB is present, it willpower the circuit.
If only 12V is present it will power the circuit.
If both are present, then 12V will power the circuit because it is higher.