Electronics Fundamentals/Electronic Regulator

Voltage Regulators

Voltage Regulators is an electronics device that has the capability to keep voltage at constant voltage level

Configurations

Zener Diode Regulator

Transistor regulator

In the simplest case emitter follower is used, the base of the regulating transistor is directly connected to the voltage reference:

The stabilizer uses the power source, having voltage U_in that may vary over time. It delivers the relatively constant voltage U_out. The output load R_L can also vary over time. For such a device to work properly, the input voltage must be larger than the output voltage and Voltage drop must not exceed the limits of the transistor used.

The output voltage of the stabilizer is equal to U_Z - U_BE where U_BE is about 0.7v and depends on the load current. If the output voltage drops below that limit, this increases the voltage difference between the base and emitter (U_be), opening the transistor and delivering more current. Delivering more current through the same output resistor R_L increases the voltage again.

Op Amp Regulator

The stability of the output voltage can be significantly increased by using an operational amplifier:

In this case, the operational amplifier drives the transistor with more current if the voltage at its inverting input drops below the output of the voltage reference at the non-inverting input. Using the voltage divider (R1, R2 and R3) allows choice of the arbitrary output voltage between U_z and U_in.

Reference

1. Voltage Regulator