I'm trying to design a very simple amplifier. I want 5W output power into 4 Ohm load. I decided to use an opamp as input stage for voltage gain. But I don't know how to build an output stage that can supply enough current. I want to use mos transistors or jfets's. The less components the better and I don't mind crappy sound. 
When you supply me an output stage could you explain the working to me?
I added an image for better understanding.
When you supply me an output stage could you explain the working to me?
I added an image for better understanding.
Attachments
Nelson Pass ZEN ?
Why dont'you look at the Nelson Pass Zen amp ?
http://www.passdiy.com/pdf/zenamp.pdf
Why dont'you look at the Nelson Pass Zen amp ?
http://www.passdiy.com/pdf/zenamp.pdf
Why not use a buffer ic ?
opamp-buffer-output stage.
A BB BUF634P you can buy at marktplaats for 2 euro.
An output stage you can build with an IRF630 and a IRF9630. and a couple of resistors.
These too can be bought at marktplaats for next to nothin.
They'll go up to 50 watts safely, and not even with crappy sound,
for like 5 euro per channel.
opamp-buffer-output stage.
A BB BUF634P you can buy at marktplaats for 2 euro.
An output stage you can build with an IRF630 and a IRF9630. and a couple of resistors.
These too can be bought at marktplaats for next to nothin.
They'll go up to 50 watts safely, and not even with crappy sound,
for like 5 euro per channel.
Attachments
Some of these might be interesting:
http://www.diyaudio.com/forums/showthread.php?threadid=35856&highlight=
http://www.ronybc.8k.com/mosfet.htm
http://sound.westhost.com/project76.htm
Although you can basically take any output stage you like/prefer.
Simplest approach (unless you go class A which you obviously want to avoid) would be a unity-gain-stable IC like the OPAxxx-series.
Then of course the opamp in front would be kind of "too much" really or you could switch it as input buffer as some people would advise to.
http://www.diyaudio.com/forums/showthread.php?threadid=35856&highlight=
http://www.ronybc.8k.com/mosfet.htm
http://sound.westhost.com/project76.htm
Although you can basically take any output stage you like/prefer.
Simplest approach (unless you go class A which you obviously want to avoid) would be a unity-gain-stable IC like the OPAxxx-series.
Then of course the opamp in front would be kind of "too much" really or you could switch it as input buffer as some people would advise to.
Douchekop said:
rather tight corner you’ve painted yourself into with these requirements
5W into 4 Ohms ~ 6.3 V amplitude, ideal class B is only 70% efficient when swinging 100% of the supply voltage on the load
a 60% efficiency requirement means with a "simple" (non-switching) output your output stage must swing to less than ~700mV of the rails and the power supply must be really close to +/- 7 V
this is possible with a complementary common source output but reliable biasing of the output devices probably takes the required circuitry beyond "really simple"
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