Transistor Amplifier Circuits Unit 8 – Transformer Coupling
UNIT 8 – TRANSFORMER COUPLING
UNIT OBJECTIVE
At the completion of this unit, you will be able to demonstrate the operation of a transformer-
coupled two-stage amplifier by using measured circuit conditions.
UNIT FUNDAMENTALS
When a transformer connects the output of the first-stage amplifier to the input of the second-
stage amplifier, the amplifiers are transformer-coupled. The transformer matches the high output
impedance of the first-stage amplifier (Q1) with the low input impedance of the second-stage
amplifier (Q2). A transformer-coupled amplifier uses less power than an RC-coupled amplifier
does because the dc voltage drop across a transformer winding is less than that of a collector
resistor, permitting a smaller dc supply voltage.
The frequency response of a transformer-coupled amplifier is normally poorer than that of an
RC-coupled amplifier.