50W mosfet amplifier IRF540/IRF9540

[apexaudio]

Amplifier based on Sony schematics.
50/100W 4/2R (20Hz-20kHz, 0,04% THD)
5Hz-50kHz +0,5/-3dB
THD 0,005% (1kHz, 4R)

[wahab]

Mile , there some mistakes on the schematic..

[soekris]

Input impedance: 220 ohm, hope it's driven from another power amplifier :-)

Or maybe you should consider using the non-inverting input ?

Soren

[apexaudio]

Originally Posted by soekris

Input impedance: 220 ohm, hope it's driven from another power amplifier :-)

Or maybe you should consider using the non-inverting input ?

Soren

Not my design, OP amp driven input.

[apexaudio]

Originally Posted by wahab

Mile , there some mistakes on the schematic..

It is unusual, not my design. Quadral use similar design but with three pair mosfet on +/-90V.

[apexaudio]

There is part of original schematics. This is experimental amplifier. Any suggestion will be welcome.
Regards Mile

[apexaudio]

Quadral use higher value for feedback resistor to get higher input impedanse, or will be better to use noninverting input? Can this simple circuit have Sonys figures? It's remande me on Hafler preamp DH101.

[nigelwright7557]

Originally Posted by apexaudio

Amplifier based on Sony schematics.
50/100W 4/2R (20Hz-20kHz, 0,04% THD)
5Hz-50kHz +0,5/-3dB
THD 0,005% (1kHz, 4R)

I reckon you could get 300watts peak with a higher voltage rail.

If the MOSFET's are 150w and they only conduct on half cycles then that is 300watts per half cycle each MOSFET can stand.

[apexaudio]

Originally Posted by nigelwright7557

I reckon you could get 300watts peak with a higher voltage rail.

If the MOSFET's are 150w and they only conduct on half cycles then that is 300watts per half cycle each MOSFET can stand.

First thing interesting to me when I see Sony schematics is useing IRF540/IRF9540 in fully simetry design, and low THD. It's good circuit for playing and experiment.

[Rikard Nilsson]

Originally Posted by apexaudio

Quadral use higher value for feedback resistor to get higher input impedanse, or will be better to use noninverting input? Can this simple circuit have Sonys figures? It's remande me on Hafler preamp DH101.

If you can live with an input impedance that low then using the inverting input can improve distorsion figures a bit. This is because the input transistors operate close to current controlled rather than voltage controlled.

But I don´t think this would be more than just measurable. On the other hand, lowering the values of the feedback resistors would improve speed and stability.

Also, I would add identical resistors to the two input transistors where the collectors are tied to the supply rails now.

Then, add an extra VAS transistor between the new resistors and the current VAS emitter. The "new" collectors should be grounded. This way, the VAS operates fully differential and distorsion is likely to drop significantly!