Power Supply Regulators Unit 4 – Voltage Feedback Regulation
Exercise 1 – Voltage Feedback Regulator Operation
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to demonstrate the operation of a
voltage feedback regulator. You will verify your results with a multimeter.
DISCUSSION
- The major functions required by a voltage feedback regulator are feedback, error detection,
and a series control element (pass transistor). - Feedback voltage is generated by the series resistors R6, R7 (a potentiometer), and R8.
- The zener diode provides a reference voltage.
- The error detection amplifier (Q3) compares the feedback voltage against the reference
voltage. - Q1 is the circuit pass transistor. The base current of Q1 is controlled by Q3.
- The regulating mechanism of this circuit consists of the base current of Q1 and the collector
current of Q3. - If the output voltage increases, the collector current of Q3 increases causing a decrease in the
base current of Q1. Q1 collector-emitter voltage increases and restores the output voltage to
the initial value.