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PostPosted: 12 Dec 2015, 12:47 
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Joined: 31 Dec 2008, 15:34
Posts: 441
Next i want to make a simple OP amp driver into a MOSFET cl. a/b amp. I've found a schematic on the internet called "Power amplifier 12W FET".

One problem ...i can't find a printboard layout for it, or even better a finished printboard, please tell me if anyone knows of the printboard.

Next problem, look at the bottom MOSFET, i think it's placed 180 degrees wrong. I would say the source of both transistors should meet and also the drains of both, should go to + and - to be a normal PP setup, right ?



Output Power 12W in 8? (max)
Input sensivity 3.2V rms (max)
T.H.D 0.002% (1KHZ)
Frequency Response DC - 100 KHZ (-3dB)

Part List:

R1= 33Kohm
R2= 6.8Kohm
R3= 22Kohm
R4= 100Kohm
R5-7= 1Kohm
R6= 330ohm
R8-11= 10Kohm
R9-10= 0.47ohm 2W
C1= 1nF 63V
C2-5= 47uF 40V
C3-4= 100nF 63V
C6= 4.7pF ceramic
C7-8= 100uF 40V
D1-2= 18V 0.5W zener
D3-4= 1N4148
Q1= 2SK135
Q2= 2SJ50

PostPosted: 12 Jan 2016, 09:14 
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Joined: 02 Mar 2009, 12:41
Posts: 1111
Location: Vänersborg, Sweden
Yet another problem, the FETs 2SJ50/2SK135 are very unobtainable today. I bought two pairs from China a few years ago, and that sort of guarantees that they may be fake (but cheap).
Look for something more modern! ;)


“If you don't know where you are going, any road will get you there.”
―Lewis Carroll

PostPosted: 23 Jan 2016, 08:39 
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Joined: 31 Dec 2008, 15:34
Posts: 441
I guess i'm very lucky then. My stock of sk135/sj50 was bought around 1988. They're 100 % genuine japanese Hitachi's. It was a time before cheating chinese copyist manufacturer of semiconductors, were in game.

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