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Registered Member #941
Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497
Not really hv related so i'll but it here.
Basically im working on a audio amplifier using jfets in the input stage and lateral mosfets in the output stage. Power output between 25 and 50 watts and a simulated THD of around 0.0005% and a frequency response from DC to a few hundred kHz.
Schematics with simulation results:
And a video:
So far its only a monaural hackjob of a prototype that needs some work.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
Just curious.....
what do you need such a high bandwidth for? ... it's likely that you will pick-up and amplify broadcast rf stations, electrical noise etc. ... you will need good input AND output filtering
Where will you get loudspeakers or headphones that justify the THD specification?
In the days when I had good hearing, if an audio PA had reasonable thd and bandwidth the next most important parameter (to my ears) was 'damping', i.e. low output impedance. A low output impedance amplifier 'controls' the loudspeaker movement well. Does your design have low output impedance?
Registered Member #941
Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497
Cadded a board to make it more production model like:
The protrotype has minimal filtering on input and output and its dead silent with no signal, all it does is about 60mV dc offset which can be adjusted down if wanned.
With my laptop as source i can see the soundcards noise when i turn the scope down to 20mV/div with a X1 probe on the speaker output.
Registered Member #941
Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497
This is for home use only in my stereo rig, i build amplifiers for fun. However on this one i may offer kits in limited numbers if it turns out working over my expectation.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
How do you regulate the operating point (idle current) of the output FETs? It is my understanding that gate threshold voltage and transconductance vary wildly with temperature.
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Amplifier with jfets and laterals
