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Analog IC Design Lab: CS Amplifier With Active Load

The document describes an analog IC design lab experiment with the following objectives: 1) To simulate a common source amplifier with a diode connected PMOS load. 2) To simulate a common source amplifier with a current source load. 3) To simulate a push-pull common source amplifier. The document provides the theory of operation for each amplifier configuration and includes the schematics and expected output waveforms. The result is that common source amplifiers with different load types were successfully designed and simulated in LTspice.

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anmol agarwal
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210 views5 pages

Analog IC Design Lab: CS Amplifier With Active Load

The document describes an analog IC design lab experiment with the following objectives: 1) To simulate a common source amplifier with a diode connected PMOS load. 2) To simulate a common source amplifier with a current source load. 3) To simulate a push-pull common source amplifier. The document provides the theory of operation for each amplifier configuration and includes the schematics and expected output waveforms. The result is that common source amplifiers with different load types were successfully designed and simulated in LTspice.

Uploaded by

anmol agarwal
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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Analog IC Design Lab

Experiment 3

Objective:To find the small signal gain (Given that W/Ln=2, W/Lp =1 and V(effective) =0.3V)
a) Diode connected (PMOS) common source amplifier.

b) Current source load single stage common source amplifier.

c) Push-pull type single stage common source amplifier.

Software Used : LTspiceXVII

Theory:

CS Amplifier with Active Load :

A MOSFET can operate as a resistor if its gate and drain terminals are shorted. This type of
configuration is called as diode connected resistor as shown in Figure below.

In CMOS technology it is difficult to fabricate resistors with tightly controlled


Av=-gm1*values of physical size.
o1||Ro2)
Hence the load resistor RD is replaced by the MOS transistor.
Ro2= (1/gm2)||ro2
Now consider the CS amplifier with diode connected load shown in figure below.

Gain will be:-

Av=-gm1*(Ro1||Ro2)

Ro2= (1/gm2)||ro2
Av = -gm1*1/gm2 (approx.)

a) CS Amplifier with Current Source Load :


In applications requiring a large voltage gain in a single stage, the relationship Av=-gm*Rdsuggests
that we increase the load impedance of the CS stage. With a resistor or diode connected load,
however increasing the load resistance limits the output swing.
A more practical approach is to replace the load with a current source.

Figure below shows the circuit diagram of CS amplifier with current source load. In this a current
source is made by using a PMOS transistor operated in saturation mode by using a Gate bias V b.

Push-pull type single stage common source amplifier:


A push-pull amplifier is a type of amplifier that can drive current in either direction through the load.In
terms of distortion and performance, push-pull amplifiers are more efficient than single-ended
amplifier because of its push-pull arrangement.In this arrangement, one transistor amplifies the positive
half cycle whereas another transistor amplifies the negative half cycle of the signal i.e. whole signal is
amplified at the output.The output stage of a typical push-pull amplifier comprises two identical
Mosfet’si.e, one source current through the load while another sink current from the load.

Schematic and Output wave forms:

A) Diode connected (PMOS) common source amplifier.

B) Current source load single stage common source amplifier.


C) Push-pull type single stage common source amplifier.
Result: Hence a common source amplifier with different load was successfully designed
and plotted.

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