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[SOLVED] MOSFET instead of planar resistors

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Zak28

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Is it fine to employ to220/247/3P MOSFETs as resistors inplace of similarly packaged planar resistors for constant loads and for switched loads?

The NMOS would be biased with a precision pot at its gate using a DMM from power supply to drain to make the current precise.

Constant load.

load.png


Switched load.

nmos-load.png
 
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1. Don't expect stable current in this circuit due to temperature dependent Vgs/Id characteristic. Some kind of feedback suggested.
2. Consider reduced power rating of MOSFET in linear mode caused by inhomogeneous current distribution. Check SOA in datasheet.
 
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FvM said:
1. Don't expect stable current in this circuit due to temperature dependent Vgs/Id characteristic. Some kind of feedback suggested.
2. Consider reduced power rating of MOSFET in linear mode caused by inhomogeneous current distribution. Check SOA in datasheet.
Click to expand...

What feedback arrangements are there without high speed opamps?
 

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