MULTISTAGE AMPLIFIERS Name of coupling Name of multistage amplifier 1) RC coupling R-C coupled amplifier 2) Transformer coupling Transformer coupled amplifier 3) Direct coupling Direct coupled amplifier

1. MULTISTAGE AMPLIFIERS

2. MULTISTAGE AMPLIFIERS
• Two or more amplifiers can be connected in a cascaded
arrangement with the output of one amplifier driving the input
of the next. Each amplifier in a cascaded arrangement is
known as a stage.
• The basic purpose of a multistage arrangement is to increase
the overall voltage gain.
• A transistor circuit containing more than one stage of
amplification is known as multistage transistor amplifier.

3. • In a multistage amplifier, a number of single amplifiers are
connected in cascade arrangement i.e. output of first stage is
connected to the input of the second stage through a suitable
coupling device and so on.
• The purpose of coupling device (e.g. a capacitor, transformer
etc.) is (i) to transfer a.c. output of one stage to the input of the
next stage and (ii) to isolate the d.c. conditions of one stage
from the next stage.
• Fig. shows the block diagram of a 3-stage amplifier. Each
stage consists of one transistor and associated circuitry and is
coupled to the next stage through a coupling device. The name
of the amplifier is usually given after the type of coupling
used. e.g.

4. • Name of coupling Name of multistage amplifier
1) RC coupling R-C coupled amplifier
2) Transformer coupling Transformer coupled amplifier
3) Direct coupling Direct coupled amplifier

5. Multistage Voltage Gain

6. Example

7. Capacitively-Coupled Multistage Amplifier

8. Loading Effects
AC equivalent of first stage in Figure
, showing loading from second stage input
resistance.