# beta gain transistor

Discussion in 'General Electronics Chat' started by fourty, Jun 15, 2014.

1. ### fourty Thread Starter New Member

Oct 13, 2013
13
0
Hi , i want to know the beta value of my 2n2222 transistor at vce=4v and ic=200ma..in datasheet the manifactor indicate that for ic=150ma and vce=10 the value of beta gain will be between 100 and 300??

2. ### ericgibbs AAC Fanatic!

Jan 29, 2010
3,324
591
hi 40,
The Beta values quoted in the 2N2222 d/s are only typical, you would have to measure the actual value to find the Beta of a transistor.

Are you using the 2N2222 as an amplifier or as a switch.

E

3. ### crutschow Expert

Mar 14, 2008
16,503
4,439
There is a wide manufacturing variation of transistor beta so you need to allow for that in your design. Normally that's done by designing the circuit to work with the minimum beta value and using negative feedback (such as with an emitter resistor) to stabilize the circuit gain (for linear amplifier applications). For switching applications you normally use a beta value of 10, independent of the stated transistor beta, to insure the transistor is fully turned on (saturated).

4. ### fourty Thread Starter New Member

Oct 13, 2013
13
0
i'm using the 2n2222 to design a class A amplifier .I want to calculate my power gain wich depends on beta value ,i set the current at Ic=200ma and Vce=4v what should i do?

5. ### fourty Thread Starter New Member

Oct 13, 2013
13
0
crutschow the power gain depends on beta value how to stabilize that??ap gain is equal to (Ap=beta*Rc*ic0/Vt)

6. ### ericgibbs AAC Fanatic!

Jan 29, 2010
3,324
591
hi 40,
The rated dissipation of the 2N2222, at 25C is only 625mW according to the datasheet.

As a Class A amplifier with Vce = 4V and Ic =200mA thats 4V * 0.2A = 800mWatts.

What bandwidth is the Class A, BJT amp required to amplify.?

E

7. ### Veracohr Well-Known Member

Jan 3, 2011
600
86
You should design a voltage amplifier with lower current then follow it with a power amplifier to handle the higher current.

8. ### #12 Expert

Nov 30, 2010
17,884
9,283
The usual way to do this is to design a circuit that really doesn't depend very much on the beta of the transistor. Do you have a schematic of what your idea is? We can work with that pretty well.

ps, that 150 ma number on the datasheet is for a pulse that is .0003 seconds wide. This transistor will not survive 0.8 watts for more than a few seconds.

• ###### 2N2222.pdf
File size:
308.1 KB
Views:
10
Last edited: Jun 16, 2014
9. ### #12 Expert

Nov 30, 2010
17,884
9,283
This is kind of the shape of a class a amplifier. Maybe you can work with this in MSpaint.

File size:
5.6 KB
Views:
103