Transistor bias configuration

@ M Sridhar
You have hijacked someone else's thread. That' considered bad practice. You should start your own thread in the appropriate forum if you expect help.

 

In answer to your question, Googling "transistor biasing" gives lots of hits for tutorials and other educational resources to help you.

 

The way a transistor works is not affected by the way it is biased. A transistor responds to voltage on its input and output, and does not care how that voltage is developed.

The applications are countless and limited only by the imagination.

Ratch

 

Sorry Ratch, I couldn't resist it.
Everything anybody would ever want to know about transistors is here.

Martin

 

"The way a transistor works is not affected by the way it is biased. A transistor responds to voltage on its input and output, and does not care how that voltage is developed."

Completely wrong.

The way a transistor works is GREATLY affected by the way it is biased. A transistor responds to CURRENT on its input.

See http://www.talkingelectronics.com/projects/TheTransistorAmplifier/TheTransistorAmplifier-P1.html

 

Your link points to a somewhat long thread. With which posts in that thread do you agree? Not every post in that thread contains correct information.

Ratch

 

No, you are wrong about that. And so is "Talking Electronics" if they aver that. Here is the reason why. Once a transistor is fabricated, nothing anyone can do externally will change its internal operation. It will operate the same way no matter what circuitry or voltages are attached to it. This principle is analogous to an op-amp. By attaching various components to the inputs and providing feedback from the output, you can make just about any electronic function you can imagine. But, now you have a circuit containing an op-amp, not just the op amp alone. The op-amp, by itself within the circuit, still acts like a dual high gain amplifier. So it is the op-amp circuit that provides the electronic function it is designed to do, not just the op-amp itself. In other words, the op-amp is not manufactured to be an inverting-amplifier or whatever else. The circuit itself is what makes a particular amplifier. Similarly, a transistor by itself is a transconductance amplifier, not a current amplifier. It can be made into a current amplifier circuit by adding a lot of resistance in its base circuit or driving it with a current generator which, in effect, adds a lot of resistance to the base circuit. So a transistor by itself is not a current amplifier for the reason that it responds to its base voltage. The base current is a indicator of the collector current, but it does not control the collector current. The physics of the BJT prove that.

Ratch

 

To be honest it was a fascinating thread to read. It was clear that physics had an advantage.
But to say "which posts I agree with" would be unfair. I wouldn't want to appear BIASED!

Martin

 

Reading some of these replies makes me want to pop some corn and crack open some beer. Then I'm going to sit back and enjoy the bloody carnage. Unfortunately the OP is going to be left more confused than when he posted the question.

Chris

 

If the OP asks an involved and open question, he/she has to be prepared for a indefinite answer and a possible involved discussion afterwards..

Ratch

 

@M.Sridhar , if you mean collector feedback biasing, as in the diagram below, it's based on the current gain of the transistor.

The relevant formulae are on the diagram, and you will find much more information on transistor biasing here:-
http://www.electronics-tutorials.ws/amplifier/transistor-biasing.html
and here:-
https://en.wikipedia.org/wiki/Bipolar_transistor_biasing

 

As I stated, I'm just going to sit back like a Roman watching a Colosseum spectacle.

Chris

 

With a certain vintage in hand to marinate ones grey matter!!

Martin

 

Then of course there is a few types of transistors all having different characteristics, current bias to voltage bias.
Bi-polar.
Mosfet.
BJT etc.
M.

 

There are no professional gladiators in this Colosseum, except, possibly for the moderators. Entertainment here is provided by spectators willing to jump down on the blood & sand to make the good kill. Also, the zombies will rise again! How many times do you need to kill the same zombie before it becomes just a boring chore?

 

Indeed that is true; which is why BJT bias networks are designed to forward bias the base-emitter junction with a current in order to have the junction develop the corresponding voltage. As you said, the transistor doesn't care. Circuit designers do not care much what particular value Vbe actually is, just that it is one standard diode drop. Transistor biasing does not control the junction voltage, it controls the base current.

 

ERM,

Hehe, this is fantastic. But should really remain here.
I admire you for sticking by your guns. I will continue to read that thread. Although it is over my head, it really is a good thread to get your teeth into,

Martin

 

Yes, one can set the base current by making Vbe comply with the desired value. As long as it is realized that the Vbe is controlling the base and collector current even if the value of Vbe is unknown at the base current value. It is ambiguous to say that the voltage or current is being biased because they are in a one to one relationship with each other.

Ratch