Transistor base Current

[windozeuser]

How Do you Find The Right Resister to use, for the transistor BASE, and to calculate the Base and collector current, is there a modified ohm's law formula?

any help is greatly appreiated

 

[samcheetah]

here are the formulas for the common collector configuration

IB = (VBB - VBE) / RB

where VBE = 0.3 for germanium and 0.7for silicon

IC = BETA * IB

VCE = VCC - IC*RC

if u know BETA and the desired VCE and IC (which u should know) u can calculate the values for the resistors i.e RC and RB

i hope that helped

 

[Roff]

If you want to use the transistor as a switch, the accepted rule of thumb is to make Ib=Ic/10. You can calculate Ic and Ib by Ohm's law.

 

[ljcox]

If you want to use the transistor as a switch, then the 2 replies you have already received are correct. But if you want to use it as an analogue amplifier, then the answer is a bit more complicated. Too complex to explain here.

If this is the case, send me an email and I'll help.