JFET/MOSFET Pentode Emulation

[POTL]

Hello
Everyone knows that with the help of a field-effect transistor it is possible to simulate the operation of a triode, it is now actively used to create amplifiers in a box
But such circuits mimic only the work of the preamp
The terminal amplifier uses pentodes, there are not enough leads for simulating the transistor, are there ways of combining the transistor as mu-amp or something similar to simulate a pentode?

[R.G.]

This is one of those (few) things that plate curves and drain curves are useful for.

The plate curves of a pentode show a lot of relatively flat I vs V territory at constant grid voltage. It's one thing that makes pentodes very useful as amplifiers.

The shape of MOSFET drain curves is a really good mimic of the plate curves of a pentode, excepting only that it has an enormously higher transconductance and much smaller "saturation" region.

So MOSFETs, except for the scaling problems, already act very much like pentodes. Much, much more than JFETs act like triodes.

[PRR]

> pentodes, there are not enough leads for simulating

The vacuum pentode needs extra wires to do things the MOSFET already does internally.

I can't agree that sand-state is a convincing replacement for hot empty bottles.

[amptramp]

The square-law variation of drain current with Vgs in a MOSFET or JFET tends to create a lot of second harmonic distortion whereas the variation is more gentle with tubes and creates more of other harmonics.  You can arrange a circuit with feedback to operate a FET so that its characteristics are close to tube characteristics but it becomes a case of getting all the harmonics to be created in the same proportion as tube harmonics.  It can be approximated and it has been done well enough to satisfy some users, but getting a FET circuit to emulate a tube from a purist's standpoint is not possible.

[tca]

> field-effect transistor it is possible to simulate the operation of a triode.

With a field-effect transistor it is possible to simulate *some parts* of the operation of a triode, not all.

[merlinb]

You need a 4-pin MOSFET with access to the substrate to get anything vaguely similar to pentode operation in an MI amp, so you can dynamically bias the substrate to emulate screen compression.

[tca]

The hard part of all of this "emulation" is in red. Not the quadratic part for small Ia but the dependence on the higher orders derivatives of it (flatness) as Ua increases.

[POTL]

thanks for answers
Is it possible to share a link to the diagram for an example?
I will explain that I am not going to replace the tube with a FET, I want to try to assemble an amplifier on FETs, I really liked the Roland Jazz Chorus circuit, but there the amplifying part is assembled on bipolar transistors

[printer2]

Nothing wrong with being bipolar. 

[mac]

I will explain that I am not going to replace the tube with a FET, I want to try to assemble an amplifier on FETs, I really liked the Roland Jazz Chorus circuit, but there the amplifying part is assembled on bipolar transistors

A power mosfet, 2sk1058 or MTP3055, and an output transformer can do it.
Will it sound like a tube amp? [...]

Nothing wrong with being bipolar. 

A lithium NPN

mac