Class A power amplifier design

Discussion in 'The Projects Forum' started by ishaan3731, Mar 1, 2012.

Jun 23, 2011
43
1
my teacher has given me a design problem :
Design a class A
1)series fed
2)transformer coupled
power amplifier that gives output of 3 W.....

conditions:
1) use only 2N176 transistor
2)amplifier must be single stage
3)just paper work required no need of practical implementation.
4)use voltage divider biasing.

please help me .....i dont know that what values i must assume in my calculations and what values i have to get from datasheet of transistor .......plz help....

2. #12 Expert

Nov 30, 2010
16,665
7,310
I'd start with the voltage limit of the transistor, but I am having no luck finding a datasheet. Can you post a datasheet?

3. lightingman Senior Member

Apr 19, 2007
374
22
2N176? This is a bit behind the times. The 2N176 is an old obsolete, germanium power transistor.
These teachers need to get to grips with technology, and bring the subject up to date.

Dan.

4. Experimentonomen Member

Feb 16, 2011
331
46
Indeed. Cant even find a schematic for audio where its used.

5. Audioguru New Member

Dec 20, 2007
9,411
896
Philips made a transistor amplifier in 1955 that used germanium transistors and had an output transformer.
Geez, that was 57 years ago.

My 1971 Philips colour TV used a class-A transistor amplifier and an output transformer.
That was 41 years ago.

Newer radios and amplifiers use silicon transistors or ICs and are efficient. They use low distortion class-AB, are not a class-A distorted heater. They do not use an output transformer.

Jun 23, 2011
43
1
i think my teacher has given me a prehistoric kind of design problem......yuckkkkk.....

Luckily i have found the datasheet........and by its looks it seems to appear that this trasistor is really an oldy goldy!!!!!

Actually i just wanna know what parameters among Rc,Re,R1,R2,Ic,Ib,Vce,Vbe,Vcc,Vout,Vin....etc(if i am forgetting any) i have to assume and which i will get from the datasheet i have attached!!!!!

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7. Audioguru New Member

Dec 20, 2007
9,411
896
We work with modern parts that work well. They have very detailed datasheets.

Why don't you ask your teacher to explain the prehistoric parts? Those very old parts do not even have a datasheet, just a few maximum spec's.

8. #12 Expert

Nov 30, 2010
16,665
7,310
30V .5A, 90W, .4 VceSat

Assume that a transformer on the output will cause the applied voltage to double at the collector of the transistor. That makes the power supply less than 15V. Try 12 volts. That makes the idle current .53 amps because .53A is the peak current of an 8 volt rms sine wave doing 3 watts. for P=IE, 3Wrms = .375A x 8V

That's a start. See if you can polish it up a bit.

9. Experimentonomen Member

Feb 16, 2011
331
46
Good luck finding the transformer, it needs to be airgapped just like the transformer for single ended tube amplifiers.

10. #12 Expert

Nov 30, 2010
16,665
7,310
That's exactly what I was thinking because I've designed and built single ended tube amps. (Antique Electronic Supply, Tempe Arizona)
However, the assignment does not require real parts. It is only to be done on paper as noted in the first post.