JFET Symmetric HP-Amp, LSK170A+LSJ74A
JFET input,
ZVN ZVP VAS,
IRF610+IRF9610 output.
Supply = +/-16VDC, 2x12VAC Transformer.
Simplified schematic here to begin with.
JFET input,
ZVN ZVP VAS,
IRF610+IRF9610 output.
Supply = +/-16VDC, 2x12VAC Transformer.
Simplified schematic here to begin with.
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For a headphone amplifier, I'd recommend a 2x16VAC power transformer and voltage regulators on the supply rails. That'll get you well regulated ±16VDC rails, even with 10% mains sag and, at the same time, "high Vin to Vout voltage drop" regulator circuits.
Where do you see cascodes? It's classic (like F5) circuit, with complementary source follower..
Btw I dont think offset will be stable without cap in the feedback loop or servo.
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> DC stable if done right.
By that I meant not 1:1 as shown in post #1.
But then it is also a "simplified schematic".
And using IRF610 & the like will mean you lose 5~6V output headroom from rail either side.
Which is why laterals or 2SK2013 / 2SJ313 are more attractive in this particular application.
Patrick
By that I meant not 1:1 as shown in post #1.
But then it is also a "simplified schematic".
And using IRF610 & the like will mean you lose 5~6V output headroom from rail either side.
Which is why laterals or 2SK2013 / 2SJ313 are more attractive in this particular application.
Patrick
But we can add bootstrapped gate drive like attched.
My library lacks of ZVP's, so BJT shown just for example.
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Woo hoo, recovery after a clipping event might be seriously "entertaining" thanks to those 470 microfarad capacitors.
Ah, no, this capacitors mostly is just a way to jump over the rails for a gate drive.
Clipping behaviour are very nice to my eyes, just stick to rail at any depth.
Potent bandwidth for used FETs and bias current.
But with a LatFETs this approach easily allows to fully saturate OPS devices, it naturally jumps over power rails without additional windings, diode bridges, regulators.
Which instead becomes too complicated for me.
😉
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This approach deserves some comments.
For headphones this would be an interesting sounding amplifier.
For headphones this would be an interesting sounding amplifier.
With easy.
Such a drive circuit just bootstrappes gate drive with output voltage. 470u will be orders more than enough to drive ~300-500 pF lateral gates.
Also there are common base driver which are free from oscillating to capacitive load such as gate.
And they are very easy to predrive because of relatively high R9+R12.
Also Q2+Q3 works with relatively small voltage drop and can provide up to dozens mA current to gates, so you will have very fast OPS, mostly limited by laterals gate resistance.
Have no doubt, this is a very underestimated OPS topilogy.