Semi-good point. In this case it's a step-up converter with diode steering, so the converter power won't be more than a Schottky diode drop down from the input power.
And it's for a battery charger: if the battery voltage is below the highest expected input voltage then the cells are toast anyway, and the proper thing to do is to not turn on at all.
You can't dump the fet. The cheap CMOS RR opamps just take 5V supply and Tim needs up to 12V IIRC.
our
Tim,
if you are going to chop stabilize the system (good idea) then you might be able to get rid of all the op amps and transistors, just take the two sides of the current sense resistor and voltage divide them both down to a suitable range to input them both directly into 2 of the uP A/D inputs. You can do the subtraction in software and turn off the output as you suggest to zero the whole mess. And if you want to you can connect a known load that pulls a known current to calibrate the gain. (maybe just once in production). If you calibrate the offset and gain this way, the two dividers don't have to be accurate or even matched. They have to just be stable.
Mark
Then use a cheap bipolar RR opamp.
John
Firefox V3.6 has no problem with it. I'll try 5.
Just get 6 and be done. Mozilla ain't no dummies.
It seems to be more of a firewall issue than a browser thing.
John
Would not a portion of the log amp circuit I posted for you give you this outcome?
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