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-   -   emulating a lateral mosfet (http://www.diyaudio.com/forums/solid-state/136249-emulating-lateral-mosfet.html)

hitsware 10th January 2009 03:42 AM

emulating a lateral mosfet
 
If you added a source resistor to a IRF510 ....
What value would make it temperature stable
@ ~ 100 mA ..... ?

djk 10th January 2009 10:56 PM

The Vgs are so different, the pin-outs are different too.

The transition on the Rds vs temperature is not going to be changed by an external resistor anyway.

hitsware 11th January 2009 01:11 AM

O.K.
Let's take a bi-polar xsistor.
With enough emitter resistance
they can run warm without runaway
due to the voltage drop accross the
resistor (as current goes up)
debiasing the active device enough
to compensate.

Same should work with a mosfet (enhancement mode)
right ?

djk 11th January 2009 02:53 PM

"Let's take a bi-polar xsistor.
With enough emitter resistance
they can run warm without runaway
due to the voltage drop accross the
resistor (as current goes up)
debiasing the active device enough
to compensate."

BJTs still need a bias compensation circuit, even when running the outputs in pure class B. Examples of this might be the Crown and Phase Linear amplifiers, both of which run only 0.34V on the bases of the outputs and still have thermally coupled bias circuits.

If you are planning on running class A you may be able to get away without proper thermal tracking.


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