q-point of a transistor ..help

Thread Starter

herbgriffin

Joined Feb 14, 2011
11
we are tasked to make a bjt amplifier, and i don't know what values of Ic,Vce ..Rb and Rc and other values....because i don't know how to find the operating point of the transistor....
 

Audioguru

Joined Dec 20, 2007
11,248
You cannot buy a transistor that has a specific beta of 69.28. So we design circuits for a transistor that has a typical beta of 69 but could have beta from 35 to 140. Then any transistor with that part number will work.

You need a voltage gain of 200 so the load resistance must be very high or use more than one transistor.
 
Last edited:

Adjuster

Joined Dec 26, 2010
2,148
It may be easier to obtain the required voltage gain and output swing if you use a rather bigger supply voltage than you might at first think necessary. The voltage would of course need to be suitable for the transistor used.

An adequate supply voltage will allow you to use a big enough collector load to obtain the required gain. If possible, it might be better to use an even larger load resistance so that somewhat more voltage gain is available, and then to set the gain to the required level by inserting a small additional (undecoupled) emitter resistance.
 
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