(i) A single stage amplifier consists of one amplifying device (VT, BJT, FET, or op. Amp)
(ii) A biasing network
(iii) Coupling ckts.
To achieve larger amplification and desired input and output resistance two or more single stage amplifier are connected in cascade.
Classification of Amplifier
Amplifiers are classified as:
(1) According to the numbers of stages used
(a) Single stage amplifier
(b) Multi stage amplifier
(2) According to the methods of operation, amplifiers may be classified as
(a) Class A Amplifier
(b) Class B Amplifier --> used with untuned power amplifiers
(c) Class AB Amplifier --> used with untuned power amplifiers
(d) Class C Amplifier --> used with tuned radio-frequency amplifiers.
The position of the Q-point on the device characteristic and the extent of characteristics being used deter genes the method of operation of an amplifier.