I have done this umteen times in real circuits decades ago.
Best to try it yourself to be convinced.
Don't take my word.
Cheers,
Patrick
Best to try it yourself to be convinced.
Don't take my word.
Cheers,
Patrick
Oh, I believe you. It's just that that still leaves me not understanding why it is. 🙂
Cheers,
Jeff.
Cheers,
Jeff.
The positive tempco of JFETs are nowhere as bad as BJTs.
They also have less gm / transconductance.
Patrick
They also have less gm / transconductance.
Patrick
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Sorry, my question was academic, I was just thinking about the control loop with two (or more) devices and the best way to control them - as a whole or individually, each has its drawbacks.
As for the J2, the PCB's Iv'e ordered have a single output - hope there's not too much debugging 🙂
Oops, Just spotted J3a drain not connected
As for the J2, the PCB's Iv'e ordered have a single output - hope there's not too much debugging 🙂
Oops, Just spotted J3a drain not connected
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If you wish to control the two current sources exactly, both for bias and for dynamic current modulation, then you should use separate optocouplers.
They are then only connected at the speaker ouput.
And then they do not need to be matched, whereas the Semisouth's still have to be.
Academic, as you said.
Patrick
They are then only connected at the speaker ouput.
And then they do not need to be matched, whereas the Semisouth's still have to be.
Academic, as you said.
Patrick
Thank you, it still leaves me wondering about the drains connected together, it changes the loop behaviour.
Toshiba MOSFETs are almost perfect penthodes.
Which means that above 4V, the drain current is essentially independent on Vds,
and only dependent on Vgs.
Patrick
Which means that above 4V, the drain current is essentially independent on Vds,
and only dependent on Vgs.
Patrick
Penny dropped, the answer to my question was obvious with one current source and multiple outputs.
With only half a brain cell, it takes me a while to chew through an idea.
With only half a brain cell, it takes me a while to chew through an idea.
My previous answers were always referring to one current source per Semisouth.
If anything, you need to limit the dissipation of each MOSFET in the current source.
Patrick
If anything, you need to limit the dissipation of each MOSFET in the current source.
Patrick
Unobtainium made available. 🙂
Interest for genuine Toshiba 2SK3497 curve tracer matched pairs & quads
Patrick
Interest for genuine Toshiba 2SK3497 curve tracer matched pairs & quads
Patrick
Yeah, they're dead all right.
Presumably:
FIRST WATT
http://www.firstwatt.com/pdf/prod_j2_man.pdf
6moons audio reviews: FirstWatt J2
Presumably:
FIRST WATT
http://www.firstwatt.com/pdf/prod_j2_man.pdf
6moons audio reviews: FirstWatt J2
Probably a stupid question, but:
The 2SK170s in the current source. They're each going to dump their Idss no matter what the other is doing, right? So a 2mA and a 6mA will act the same as two 4mA?
Cheers,
Jeff.
The 2SK170s in the current source. They're each going to dump their Idss no matter what the other is doing, right? So a 2mA and a 6mA will act the same as two 4mA?
Cheers,
Jeff.
> So a 2mA and a 6mA will act the same as two 4mA?
Yes.
But the one I posted, I use a fixed drain resistor and adjustable current source with an extra source resistor trimmer.
Guess why ?
Patrick
Yes.
But the one I posted, I use a fixed drain resistor and adjustable current source with an extra source resistor trimmer.
Guess why ?
Patrick
I thought it was so that you could use BL parts (instead of GR). But I suppose it also lets you use any part without knowing its Idss?
