Electronic Devices and Circuits: Unit II: Amplifiers
MOSFET Common Drain (Source Follower) Amplifier
The input signal is fed at the gate similar to the common source amplifier. The signal output is taken at the source terminal.
MOSFET COMMON DRAIN (SOURCE FOLLOWER) AMPLIFIER
The
input signal is fed at the gate similar to the common source amplifier. The
signal output is taken at the source terminal. The source follower using MOSFET
is shown in the Fig. 2.26.
The
small equivalent circuit for source follower MOSFET is shown in Fig 2.27.
Input Impedance
With
VS = 0 and ig = 0, the input impedance can be written as
Rm
= RG
Output Impedance
The
output impedance is given by
Voltage Gain
The
output voltage is given by
The
input voltage is obtained using voltage division as
Therefore
it is called source follower
Current Gain
The
short circuit small-signal AC current gain can be determined as follows, let ig
= 0
Properties
i.
Non-inverting amplifier
ii.
Very large input impedance
iii.
Small output impedance
iv.
Voltage gain AV ≤ 1
Electronic Devices and Circuits: Unit II: Amplifiers : Tag: : - MOSFET Common Drain (Source Follower) Amplifier
Electronic Devices and Circuits: Unit II: Amplifiers
Under Subject
Electronic Devices and Circuits
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