How to bias a CS mosfet

You're not an engineer, are you?

John

I think the definition of an "ass" is "an incompetent trying to impress"... Larkin is the Gold Standard... but Ian is struggling to catch up ;-) ...Jim Thompson

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Larkin totally missed the jab... I loved it... "paints by numbers" ;-) ...Jim Thompson

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And how's that working out for ya?

John

It's an awfully big country, and you wouldn't want to visit their parts of it voluntarily.

And they're all hot air anyhow.

John

How about this, Ian? Is this what you meant?

Version 4 SHEET 1 880 680 WIRE 192 -64 -64 -64 WIRE 320 -64 192 -64 WIRE -64 -32 -64 -64 WIRE 192 -16 192 -64 WIRE 320 -16 320 -64 WIRE 320 80 320 64 WIRE 192 96 192 64 WIRE -64 176 -64 48 WIRE 16 176 -64 176 WIRE 144 176 96 176 WIRE -64 208 -64 176 WIRE 32 256 0 256 WIRE 64 256 32 256 WIRE 192 256 192 192 WIRE 192 256 144 256 WIRE 192 272 192 256 WIRE 32 288 32 256 WIRE -64 368 -64 304 WIRE 32 368 32 352 WIRE 192 368 192 352 FLAG 192 368 0 FLAG 320 80 0 FLAG 32 368 0 FLAG -64 368 0 SYMBOL nmos 144 96 R0 SYMATTR InstName M1 SYMATTR Value IRF7468 SYMBOL res 176 -32 R0 SYMATTR InstName R1 SYMBOL res 176 256 R0 SYMATTR InstName R2 SYMBOL voltage 320 -32 R0 SYMATTR InstName V1 SYMBOL res 160 240 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMBOL cap 16 288 R0 SYMATTR InstName C1 SYMBOL npn 0 208 M0 SYMATTR InstName Q1 SYMBOL res -80 -48 R0 SYMATTR InstName R4 SYMBOL res 112 160 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R5

If I am reading this correctly, you are advocating holding a constant source current, thus a constant drain current. Yes?

If so, then Vd floats up and down with Vcc but not at 1/2 the slope.

Cloud cukooland.

I haven't got LTspice installed on this box and CBA rectifying that oversight.

More or less, but it worked perfectly OK for a 2N7000 based guitar clean boost pre-amp - but I had to split the source resistor and only decouple part of it as the stage had way more gain than I wanted.

Shooting an unarmed man in the back doesn't take a lot of substance.

Grounded base wouldn't give the required 180 deg phase change.

Because you're too thick to visualise such a seriously simple circuit and its great fun winding you up.

For a "circuit designer" you seem astoundingly clueless!

Who ties your shoelaces for you?

Don't worry about it. They are, as the Texas saying goes, all hat and no horse.

John

The feedback from the fet drain back into the gate needs to be non-inverting. So a PNP common-base transistor would work.

John