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Hmmm. 100 ohms should have been plenty low enough. I'm guessing your regular meter read the 24 volts??
Maybe 2 100 ohm in parallel and well see if it goes up to 23.5.
...
(re putting RC delay on the FET gate)...
I think you could do that on your load because it is open loop. But with the closed loop it needs to be pretty fast or it will oscillate. If we were using BJT we could run it open loop with just some emitter resistors to even up the Vbe drop of the parallel transistors, but with the wide range of threshold voltage using FETs we can't use the same method.
() how do you mix your pictures in with the text. Is it just a paste? What kind of file?
I'm tied up today, but I will try to zip up my models and attach them. There may be a few %$* ups but most are ok.
() how do you mix your pictures in with the text. Is it just a paste? What kind of file?
Hi (),
Thanks for the tip ...
... Might also be the generic FET. ...
Yeah, that was indeed what was happening. However, in the future if we want to lower the current sense resistor down to say... 50m Ohms or lower to reduce heat, we will want the lowest offset parts we can get for best stability and accuracy.I don't think it's offset so much as the LT1097 doesn't go to ground.
I tried the above simulation with all sorts of the in-built MOSFET models and most worked fine for me. The only ones that didn't really work were the last two with the highest RdsON, which is understandable. The above simulation with the STP80NF12 also works. Keep in mind though it's still not the exact right Op-Amp.Might also be the generic FET. I'll have to give it a try.
So... Remind me which Op-Amp we are using? I have the STP80NF12 model and it appears to be working...