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Another LTspice question. Vswitch bug?

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Nice switching circuit!
Here is a way you can completely eliminate the power supply sequencing, and reduce the base current error at the same time.
I used a Darlington pair because the 2N3906 beta is lower than the 2N3904.
 

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Roff,

Just a quick reply, as I'm about to head out, but I couldn't resist loading up that circuit. Wow.... The combination of that Linear tech opamp, and the (very clever!) use of the darlington.. I couldn't see any difference between 'Iout' and 'Vout'! Talk about accuracy! I realise that if one uses a 2% current sense resistor then the other errors aren't really important, but using a <0.5% resistor, that circuit design really shouldn't relaly pull it any higher, ergo: accuracy of ~0.5%. My best hope, given all the variables was 3% over the selected current range, so 0.5% is GOLD. Thanks!

I know I've kind of let this thing run away with me (its just a high side current measurement...no brand new idea's) but its great to have others help tweak and perfect circuits so they can perform as good as they can, without having to resort to extremely expensive bits of kit. If this project/thread seems to die for a while, don't worry, I have a list of projects/contracts (power supply, industrial control) which NEED decent and versatile high-side sensing -without breaking the bank, so no doubt at some point I'll put together some tried and tested circuits and post in the forum.

Thanks again guys! On the off-chance I can help with anything (doubtful, since you're both analogue gurus) PM me any time. Sometimes I forget to check the board for weeks on end, but always check my email.

BT
 
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