Transistor Amplifier Circuits Unit 9 – Direct Coupling
Exercise 3 – Direct-Coupled Amp Frequency Response
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to determine the frequency response of
a direct-coupled amplifier by using measured values. You will verify your results with a
multimeter and an oscilloscope.
DISCUSSION
- The bandwidth of a direct-coupled amplifier can extend to frequencies below 5 Hz.
- Direct-coupled amplifier frequency response is good at low frequencies because of the lack
of a capacitor in the connection path. - Amplifier gain is reduced at low frequencies because of capacitive reactance.
- The high frequency bandwidth limit is limited by frequency-dependent amplifier parameters
and stray circuit capacitance. - RC-coupled amplifiers have a capacitive reactance large enough to reduce gain at frequencies
below 50 Hz. - Transformer-coupled amplifiers have reduced gain at lower frequencies because of the
transformer characteristics.