The bandwidth of multistage amplifier is always less than that of the bandwidth of single stage amplifier.

**Frequency Response of Multistage
Amplifiers:**

The
bandwidth of multistage amplifier is always less than that of the bandwidth of
single stage amplifier.

**1. Overall Lower Cut-off
Frequency of Multistage Amplifier:**

**2. Overall Higher Cut-off
Frequency of Multistage Amplifier:**

Let us
consider the upper 3dB frequency of n identical cascaded stages as f_{H}(n).
It is the frequency for which the overall gain falls to 1/√2 (3dB) of its
midband value.

Taking n^{th}
root on both the sides,

2^{1/n}
= 1 + [ f_{H}(n)/f_{H} ]^{2}

2^{1/n}
-1 = [ f_{H}(n)/f_{H} ]^{2}

Taking
square root on both the sides,

√2^{1/n}
-1 = f_{H}(n)/f_{H}

f_{H}(n)
= f_{H} √2^{1/n} -1

In
multistage amplifier f_{L}(n) is always greater than f_{L} and
f_{H}(n) is always less than f_{H.} So the bandwidth of
multistage amplifier is always less than single stage amplifier.

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail

Electronic Circuits - Frequency Analysis of BJT and MOSFET Amplifiers : Frequency Response of Multistage Amplifiers |

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