Aleph J Schematic

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#704
You could go to DIY Chip Amplifier Kits, PCB's, Components and Information. and buy the big power supply boards he sells. He sells more than one style of power supply board so make sure you get the big ones at the bottom. $9 each if I recall. They are very good looking boards. Well layed out, cheap, and perfect for this application. They will accept 6 caps in a CRC configuration and you could get as much as 120,000uf in there, maybe more if any larger caps would fit. If you try this make sure that the diodes you use in his boards can handle the current. The board accepts TO-220 diodes.
Uriah
 
#712
I will use this schematic
 

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#713
Q3 sucks some current from the jfet - and it tries to restore always the quiescent current - how should this work???

And Q4 amplifies the voltage on the sensing resistor - what for??? To much dissipation??? We could use higher resistor value there.

I don't like the bootstrapping - what for?

Maybe you could keep q4, set the idling current with it (see pass current source) and couple the signal of the sensing resistor direct. If you use a high resistor value to couple the Q4 signal to the gate, you could "overwrite" it with the signal from the sensing resistor.

(You need a zehner diode, bridged with a cap - because of the DC voltage drop require. You could use another zty for a current source for the zehner...)

But maybe, my understanding of Q3 is wrong, and Q4 improves all stuff... But what the hell bootstrapping is for - you only need it, if your driver normally requires a higher power supply, but you don't want to pay... ;-)

Regs, Dirk
 
#715
HV. calm down.
This is almost the aleph J schematic except two red points resistors which are wired differently.
The voltage across the sensing resistor modulates the current source from the emittor of
Q4 instead of from its base (Aleph) because, compared to aleph the sensing resistor voltage is phase opposite.
Though, Wensan would speak better than i do about this as beeing his own idea.
 
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#716
Sorry, I'm just getting exited if I don't understand things properly...

That you modulate on the emitter is maybe ok. But I still do not understand that you need the two unlabeled resistors... I still feel, we could drop all the ztx stuff and replace them with the J2 like solution. I cannot see any advantage - but maybe that is only because of my bad knowledge. So sorry if you got my comments in a rough way...

Dirk
 
#717
The upper resistor is 68.2k like aleph J. I just erased the value by mistake.
The three tied are 0.47R
The resistor from base of Q4 to middle point is about 500R
I do not know precisely for the two last which i count to adjust experimentally for a8 ohm load, and /or to ask the help of Wensan.
I suggest you have a look at the Wensan thread: "Excellent SRPP power amp of MOSFET"
 
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