That 20 mA source supplies current to asymmetric class A output stage.
Bootstrapped current mirror supplies voltage between gate and source of the output device. It would be interesting to compare results with a single pnp transistor loaded on resistor between source and gate.
Chris,
Yes it's correct - see the AD797 opamp (designed by Scott Wursor). In the schematic shown, if 5mA runs through each of the resistors R5, R6 then, about 5.5mA will flow out of the Q3,Q4 emitters, leaving the remainder of the I2's 20mA to come from the output Mosfet M3. The entire circuits self biases up automatically.
Paul Bysouth
Yes it's correct - see the AD797 opamp (designed by Scott Wursor). In the schematic shown, if 5mA runs through each of the resistors R5, R6 then, about 5.5mA will flow out of the Q3,Q4 emitters, leaving the remainder of the I2's 20mA to come from the output Mosfet M3. The entire circuits self biases up automatically.
Paul Bysouth
Oh, Ok, thanks! That's cool. So the output stage isn't a follower, but rather a "transconductance output" (high Z).
Much thanks to you both,
Chris
Much thanks to you both,
Chris
Looks pretty good to me -
This is a nice design. can you give the transistor types you recommend using here, pls. Thx - RNM
This is a nice design. can you give the transistor types you recommend using here, pls. Thx - RNM
Which is exactly how i consider it as well or anyone working in corporate America. If it hasnt been done in THIS field, it is patentable.
How much emitter resistance is needed
to degenerate the gain of a 2n4401 down to
an (enhancement-version) 2sk170 ?
(since the enlightened know that bi-polars are voltage controlled)
to degenerate the gain of a 2n4401 down to
an (enhancement-version) 2sk170 ?
(since the enlightened know that bi-polars are voltage controlled)
1/22mS = 46 ohm.
And 22mS comes from first page of data sheet :
2SK170?Junction FETs (Single/Dual)?TOSHIBA Semiconductor & Storage Products Company
Mr. Wavebourn is assuming the NPN has zero emitter resistance, which is of course not 100% true.
It depends on the bias.
Patrick
And 22mS comes from first page of data sheet :
2SK170?Junction FETs (Single/Dual)?TOSHIBA Semiconductor & Storage Products Company
Mr. Wavebourn is assuming the NPN has zero emitter resistance, which is of course not 100% true.
It depends on the bias.
Patrick
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No, Hfe isn't one of the fundamentals of transistor operation, there's significant process variation.
No, Mr Wavebourn does not assume that emitter resistance is zero, as well as that beta is infinite. But I assume that 47K would be close enough.
Spec goal in design -
Here is were some spec numbers came from as goal - see line #279 of Marsh headphone amp forum.
Here is were some spec numbers came from as goal - see line #279 of Marsh headphone amp forum.
But you have been educated on this subject - you yourself said that 'the enlightened know transistors are voltage controlled' 😉 That Hfe isn't well defined is a corollary of this I believe.
Cute. Brings memories of Malcolm Hawksford.
So far the only real novelty in the barrage of 'me-too' circuitry 😉
jan
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This is a critical tool, and as I and Jung have shown elsewhere, dates back well before Hawksford to Boxall and Aldridge. Walt is working on the all-JFET history so I won't go into that here.