DEF Amp

Here is an idea for using the IXTH16N50D2 on top of an IRFP9240. Idle current simulates to 1.3A. I have these parts on hand, but probably won't have time to get around to testing it for some time to come. The Toshiba 2SJ201 also seems to work with the IXYS part. Just throwing out some ideas...
 

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Indeed. Though, they are still available from Mouser (and possibly others).

I am tempted to buy some before supplies run out since I still feel the sting from my failure to buy the Semisouth parts when they were still available from distributors after the company closed. But, without any known designs using the Infineons, the price per unit is hard to swallow...
 
Pico's simple DEF and DUMB amp

DEF%20Amp_1.png

Hello 2 picoDumbs. Have you already assembled your circuit? On turn on, the upper depletion type FET may appear as a low-Ohm power resistor until it biases properly. The path of current of ~2-3A [if any] is possibly via the loudspeaker to ground. Speculation; but it may be best during the initial study to disconnect the load or use an output coupling cap to protect it.
 
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Depending on value of input coupling and such, you will generally
see a turn-on spike the size of Vgs, or about 4 volts in my current
example.

This doesn't scare me, but it can be addressed with the offset voltage
already in place when the power comes on or by a delayed output relay.
 
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Hello 2 picoDumbs. Have you already assembled your circuit? On turn on, the upper depletion type FET may appear as a low-Ohm power resistor until it biases properly. The path of current of ~2-3A [if any] is possibly via the loudspeaker to ground. Speculation; but it may be best during the initial study to disconnect the load or use an output coupling cap to protect it.

No, I haven't built it yet, I'm in the middle of building a different amp.
I'm just throwing out ideas that other people might want to build on.

R1/R2 is intended to be a 10k Pot, and R3/R4 could be a 10k pot. I just threw it together very quickly from what I learnt from Papa.
20P20-75 is Exicon to264 packaged lateral mosfet for a bit more transconductance than the to247 device. You could use Alfet parts too.
 
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