Single Stage Amplifiers

Single Stage Amplifiers

Amplifier is  a device which increases the strength of the input signal applied. The amplification is done to improve the strength of the signal sometimes above the noise signal. Also in some cases the input signal is weak to drive a load of a subsequent stage. 

Depending upon the amount of amplification to be done, the amplifiers are either single stage amplifiers or multi stage amplifiers i.e. more than one stage say two stage or three stage etc.

In this section we will see how a MOSFET can be used as an Amplifier from the knowledge of the MOS device learned so far. 

In this section we discuss the Low Frequency behavior of single stage MOS Amplifiers

The Figure 1 shows the general Amplifier Block Diagram where input is taken as x(t) and output is taken as y(t)

The general Amplifier equation is given by:

y(t) =Ax(t) 

Here A is called the gain.

Different categories / Topologies are shown in Table.

Common Source Stage

Source Follower

Common Gate Stage


Resistive Load

Resistive Bias

Resistive Load


Diode-Connected Load

Current-Source Bias

Current-Source Load


Current-Source Load




Active Load




Source Degeneration