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I'm doing a project in which I want to use a floating-gate MOSFET to perform analogic multiplication. After calibration of the resistance generated by the FGMOS, I will simply use the voltage as input, the impedance as multiplier, and the current as output.

G·V = I

I wish to use a floating gate MOSFET for its capacity to store the resistance of the cell and use it multiple times.

However, I couldn't find any website that sells FGMOS.

I hope someone can advise me.

ocrdu
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Mayeul FORCEVILLE
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    Floating gate MOS is an element used in integrated circuits. Discrete MOSFETs that you can buy off-the-shelf are not intended or suitable for that kind of application. – John D Apr 14 '23 at 17:37
  • In your opinion it's impossible to find in the market. Mosfets are also used in integrated circuit and as you said it can be bought. Maybe there is no market for them... Sad – Mayeul FORCEVILLE Apr 14 '23 at 17:53
  • @MayeulFORCEVILLE There isn't enough demand for discrete FGMOS devices. Analog multiplication is generally done using a Gilbert cell, in the rare cases it's needed; I believe you can get some ICs based on one from TI and Analog. It would likely be more cost-effective to do in software using a microcontroller (with built-in ADCs) and a DAC. – Hearth Apr 15 '23 at 15:16
  • Mmm, the purpose of the project is mainly to see whether or not this technique can be used to perform efficient multiplication at low level power. But if it's impossible I guess I will go with a Gilbert cell thanks for the info. – Mayeul FORCEVILLE Apr 15 '23 at 17:04

2 Answers2

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If you are looking for a discrete option, you probably aren't going to find a discrete package on the commercial IC market. You'll have to have one of these fabricated on a silicon die from a company or university that has that capability.

Voltage Spike
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You might be able to make use of something like this,

https://www.aldinc.com/ald_epadnchan.php

From the application note,

[T]he EPAD allows analog circuit trimming in up to 20,000 discrete steps with 0.1mV increments. In engineering environments, the EPAD is quickly and easily programmed to fit the needs of a specific application. In test environments, it can be programmed in-system, that is, as an integral part of a circuit board assembly [...].

Unfortunately (from their FAQ),

10. Can I erase a programmed EPAD MOSFET?

No. A programmed EPAD MOSFET cannot be erased normally.

So it would work if you only need it to handle one strictly rising set of voltages and that's it.

But perhaps you are after something more specific e.g. IC design and you need something from the lab, not off-the-shelf.

Tim Williams
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    That won't work, the floating gate must have insulation around the gate to avoid long term loss. – Voltage Spike Apr 14 '23 at 18:29
  • As I understand it, that's... precisely what they do? – Tim Williams Apr 14 '23 at 18:36
  • @TimWilliams Except IIRC the gate charge is programmed at the factory, and is not meant to be changed repeatedly as the question replies. I've looked at those some time ago so not 100% sure anymore. – Kuba hasn't forgotten Monica Apr 14 '23 at 20:24
  • @Kubahasn'tforgottenMonica The zero-offset ones yeah, but these are the programmable kind. They specifically note "in system programmable". I haven't used them myself, nor is it clear what OP needs, but it seems relevant. – Tim Williams Apr 14 '23 at 22:22
  • Did no one tell that company that "epad" is commonly used as a short form of "exposed pad" aka thermal pad? That's just a confusing name for a product. – Hearth Apr 15 '23 at 04:17
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    Also, from the datasheet, "The basic EPAD MOSFET device is a monotonically adjustable device" and "A given EPAD device can be adjusted many times to continually increase its threshold voltage." It looks like there's no way to adjust the threshold *down*, only up. – Hearth Apr 15 '23 at 04:19