What is the effect of collector resistance in biasing?

Transistor Biasing ?

Inspite of my contionous efforts to learn biasing from almost 3 books and a number of online tutorials ,i am not yet completly clear about it.

Can i ever be ? If i can please tell me what are some good practical notes to read for this purpose.

What is the purpose and effect of collector resistance ? Does it effect the gain ?
If i know biaising can this be applied to all the circuits like osciilators and amplifiers in the same way .

Thanks !

Re: Transistor Biasing ?

Its a bit like ridding a bike.the more you do it the better you will get at it.

Why not setup a transistor on a bread board and actually do some transistor biasing and readings.

Collector resistance ( collector current dous effect the gain)

Barrybear.

Re: Transistor Biasing ?

About "Collector Resistor".

For example, for an audio amplifier in a Common Emitter schem, you can decide the amount of current to stablish the Operational Point (steady state) from which the output current from the circuit will change across that value (from near cero Amp, to twice the steady current value). And all this, to get a value of current that will satisfy your circuit needs, by using an input current that is too small to use for any purpose.

Now, based in what I've found out when testing some circuits:
If your input current is around the "uA" (micro Amperes), and you need at least 5 mA for drive a load, then you can calculate a collector resistor to handle 5 mA using a power supply value of Vcc, like this: (Vcc - Vce) / 5 mA , where Vce (in theory books) is Vce=0.7V, but in real transistors could be much less than that (sometimes near 0V).

And after you have your resistor to handle 5 mA, you search a transistor that in its datasheet shows a good Beta (or hfe) amplification for this amount of Collector Current (because that's what you get in datasheets, the Amplification Beta for a certain Collector current).

And after that, you can search for the base resistor value and anything else to drive your 5 mA output using low currents as source of your system.

Hope this helps a little.

Bye.

Re: Transistor Biasing ?

Dear truebs,
What u are facing, I have faced the same. So donot be bothered. Why don't you go through the ee140 webcast from Berkeley. Borderson has explained it well.
I donot know BJT' but MOS is more or less clear. You could start with single stage amplifiers.
It is a very good idea to rig the circuit up and see its performance.

Transistor Biasing ?

hi
first , yes if u know biasing concepts, u can apply to amp/osc.
also, the collector resistance is put in order to achieve voltage drop. You need ur Vce which is collector-emitter voltage to be approx Vcc/2. sayif vcc is 12V,then vcc/2=6V. so u need another 6V drop accross Rc and Re. if Re is of a higher value,then the looking impedance from base becomes (1+hfe)Re whic is high. hence Re cant be high..
So we put a slightly higher value of Rc for drop.
hope this helps
abhi

Re: Transistor Biasing ?

The explaination from abhy looks nice
try to focus at the concept of the current when varying collector resistence.

Transistor Biasing ?

You must know the main reason and idea of biasing. then there are some biasing networks for discrete and integrated circuits. the microelectronic of sedra is a good reference.
yes, if you know the bias you can apply it for any kind of circuits with small variations.

Transistor Biasing ?

yes sedra-smith's book is good.u can learn biasing from it

Transistor Biasing ?

The resistance connected to the collector represents the load in case of Common Emitter, with respect to biasing each circuit has its own biasing condition according to the purpose of the circuit.

try this link it may be usefull for u
http://www.williamson-labs.com/

Re: Transistor Biasing ?

hello
all ur confusion can be easily removed if u read boylestad chapter no3 of electronics book 7th ed

Re: Transistor Biasing ?

There are many books on microelectronics but i suggest u to read the book by millman and helkias or millman and grabel.from where u will get the complete idea of transistor biasing.
2> elctronic devices and circuits by john paul(new age publication).In this book many problems r solved which r base on transistor biasing.
3> electronic principles by malvino .from this book also u may get some help.

Transistor Biasing ?

Hey man,

starting from the scratch, collector resistance is basically used to get a voltage drop and the value of collector res. decides ur output current...n awan's post is a good one coz Boylestead is the best book for studyin basics of BJT's...hope this finds u with affirmation...

Transistor Biasing ?

i strongly suggest you to read boylestead and nashelsky

the explanations are very good

Transistor Biasing ?

from where we can obtain these books if u have it can u upload it to us

Re: Transistor Biasing ?

All suggested books are good.

But you really need to setup a small circuit. Try to change the different biasing and try to compare.