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CMOS amplifier configuration

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invent

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Can anyone provide me with a simple explanation on common-drain, common-source and common-gate configuration..espeacially on its strong point and weak points.

Or is there a source where the comparizon between these three configuration is summarized into a table:?:

Thks
 

Common Source:
Only one of the three with the possiblity of a Gain greater than 1.
Low input and output impedance

Common Drain:
Gain smaller than unity
Can be designed with very high input impedance
Low output impedance

Common Gate:
Approximately Unity gain
Can be designed with very high output impedance
Low input impedance

More info can likely be found by searching google.
 

CD you use it as a buffer
CG It has low input inpedance good for matching to antennas
CS provides large gain and large input impedance
 

these configuration are used in analog design

see Allen book
 

vortechs2k said:
Common Source:
Only one of the three with the possiblity of a Gain greater than 1.
Low input and output impedance

I guess you mean High input and output impedance.

(in this configuration, the transistor act as voltage controlled current souce where the current flows into a high output impedance=>gain)
 

Complementary metal–oxide–semiconductor (CMOS) ("see-moss", IPA: ['si.mɜs]), is a major class of integrated circuits. CMOS technology is used in chips such as microprocessors, microcontrollers, static RAM, and other digital logic circuits. CMOS technology is also used for a wide variety of analog circuits such as image sensors, data converters, and highly integrated transceivers for many types of communication.

CMOS is also sometimes explained as complementary-symmetry metal–oxide–semiconductor. The words "complementary-symmetry" refer to the fact that the typical digital design style with CMOS uses complementary and symmetrical pairs of p-type and n-type MOSFETs for logic functions.
 

see behzad razavi's book (analog cmos ic design)
in short:
cs is for gain
cd is for level shift but is not often used because its outoput impedance has inductor char.
cg is used in cascode configurations for increasing ro and improving freq response
 

Common source:

It got an infinte input impedance and hence can act as a good amplifier.. Additionally it got low output impedance..

Common gate:

It got very low input and output impedance.. The input current is more or less equal to output current and hence can be regarded as a "currect follower"..
Here there is an internal feed back resistor between the source and drain and hence can make the circuit unstable if we dont take care of it properly..

Common drain:

It has high input impedance and low output impedance.. The input and output voltage are more or less same and hence it can be called as "Voltage follower".. We can use it as a buffer and finds very useful in such applications..

Hence in general,common source is good for amplification purpose and common drain is good for buffering...

Added after 2 minutes:

vortechs2k said:
Common Source:
Only one of the three with the possiblity of a Gain greater than 1.
Low input and output impedance

Common Drain:
Gain smaller than unity
Can be designed with very high input impedance
Low output impedance

Common Gate:
Approximately Unity gain
Can be designed with very high output impedance
Low input impedance

More info can likely be found by searching google.


"Common Source:
Only one of the three with the possiblity of a Gain greater than 1.
Low input and output impedance"

Common source actually has high input impedance.. You mentioned it as low input impedance.. Watch out..
 

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