VOLTAGE REGULATORS

SECTION EIGHT

                   VOLTAGE REGULATORS

A Voltage Regulator tak es a high input voltage and delivers a fixed output voltage. Providing the input voltage is 4v above the output voltage, the regulator will deliver a fixed output voltage with almost no ripple.

Voltage regulators are also called "3-TERMINAL REGULATORS" or "REGULATOR IC's" - although this name is not generally used. In most cases, a voltage regulator gets quite hot and for this reason it has a high failure-rate.

If a regulator is not getting hot (or warm) it has either failed or the circuit is not operating.

A regulator can only decrease the voltage. It cannot increase the current. This means the current bei ng supplied to a circuit must also be available from the circuit supplying the regulator.

All regulators have different pin-outs, so you need to find the input pin and output pin and make sure the voltage-difference is at least 4v. Some regulators will work with a difference as low as 1v, so you need to read the specifications for the type you are servicing.

Some regulators are called “negative voltage regulators” and the input voltage will be negative and the output will be negative.

You need to test a voltage regulator with the power "ON". Make sure you do not allow the probes to short any of the pins together as this will destroy the regulator or the circuit being supplied.

With the power turned off or the regulator removed from the circuit, you can test it with a multimeter set to resistance to see if it is ok. If any resistance readings are very low or zero ohms, the regulator is damaged.