Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

[Moved]: Common collector, common emitter and common base

Status
Not open for further replies.

matrixofdynamism

Advanced Member level 2
Joined
Apr 17, 2011
Messages
565
Helped
24
Reputation
48
Reaction score
23
Trophy points
1,298
Activity points
7,369
The 3 terminal transistor can be connected in multiple ways, how do we know which configuration of common collector, common emitter and common base we are supposed to use?

Besides this, does the same rules apply on BJT, FET as well as JFET?
 

Audioguru

Advanced Member level 5
Joined
Jan 19, 2008
Messages
9,240
Helped
2,136
Reputation
4,266
Reaction score
1,960
Trophy points
1,393
Location
Toronto area of Canada
Activity points
58,073
When you learn about the applications of transistors then you will know which configuration to use.
Common collector has a voltage gain of 1 like a piece of wire but has a high input resistance.
Common emitter has up to a high voltage gain but has a fairly low input resistance.
Common base has up to a high voltage gain but has a very low input resistance.
Mosfets and Jfets are similar but their gate as an input has an extremely high input resistance.
 

crutschow

Advanced Member level 5
Joined
Feb 22, 2012
Messages
3,862
Helped
921
Reputation
1,840
Reaction score
908
Trophy points
1,393
Location
L.A. USA Zulu -8
Activity points
21,817
The common collector (emitter follower) stage has a high frequency response, a high input impedance, and a low output impedance.
It has a voltage gain of slightly less than one but has a high current gain.
It is useful if you need to drive a low impedance load from a high impedance source.

The common emitter stage is the one most commonly used to provide a voltage gain.

The common collector stage has a higher frequency response than the common emitter stage but requires a low source impedance so is not often used.
It is sometimes used in RF systems since the signal impedance is often is 50Ω or 75Ω, low enough to readily drive the emitter input of a common collector amp.
 

BradtheRad

Super Moderator
Staff member
Joined
Apr 1, 2011
Messages
14,070
Helped
2,796
Reputation
5,592
Reaction score
2,706
Trophy points
1,393
Location
Minneapolis, Minnesota, USA
Activity points
104,951
See my reply in a recent thread:

https://www.edaboard.com/threads/338349/

You can pick up a lot about what transistors can do by looking through books on transistor circuits for the experimenter.

Every so often I see someone making unconventional use of some characteristic of transistors, which reveals possibilities to my mind.

I learned a great deal by playing with simulations.

Also examine the multitude of transistor circuits at the website below. It shows you the benefit in the philosophy that we learn more about what's inside an IC, by duplicating its function using discrete components.

www.4qdtec.com
 

matrixofdynamism

Advanced Member level 2
Joined
Apr 17, 2011
Messages
565
Helped
24
Reputation
48
Reaction score
23
Trophy points
1,298
Activity points
7,369
Why bother about transistor amplifers? Why not just make one using op-amps?
 

LvW

Advanced Member level 5
Joined
May 7, 2008
Messages
5,845
Helped
1,743
Reputation
3,490
Reaction score
1,343
Trophy points
1,393
Location
Germany
Activity points
39,354
Because an op amp can't do everything that a transistor can.

...and a transistor can`t do everything that an opamp can.
Hence, each device has its pros and cons and its own application area.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top