# q-point of a transistor ..help

Discussion in 'Homework Help' started by herbgriffin, Feb 17, 2011.

1. ### herbgriffin Thread Starter New Member

Feb 14, 2011
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0
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....

Mar 6, 2009
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3. ### hobbyist Distinguished Member

Aug 10, 2008
774
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Please give all the parameters you need to work under,
such as load impedance, or signal voltage, power supply, ect....

4. ### herbgriffin Thread Starter New Member

Feb 14, 2011
11
0
we are given an input of 50mVpeak and expected output of 10Vpeak to peak
and beta is 69.28 ....

5. ### Audioguru New Member

Dec 20, 2007
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896
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: Feb 18, 2011
6. ### Adjuster Well-Known Member

Dec 26, 2010
2,147
300
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.