Voltage regulator/ reference

George Herold · 2019-05-10T17:56:00+00:00

OK this is an easy problem, and I'm mostly just trolling for maybe another idea/ IC. So I need a 5 V bias supply. Current ~20 mA (A little less depending on how I load it.) The voltage doesn't need to be particularly accurate, but it does need to be stable. Some of the experiments/ measurements could run over a day or two and the voltage needs to be stable over that time. How stable you ask? I'm not sure, I could do a few measurements.. but I first built the supply from a three terminal regulator (lm317l) And there was some drift that might have been the regulator. So my second idea was to use a voltage reference (already used in the circuit elsewhere) and buffer that with an opamp. (See my C-loaded opamp thread of a week or two ago.) This seems fine, but a secondary concern with the circuit is that it's going to be hooked up by students and I worry about some one hooking it up wrong and cooking the opamp. So I've been noodling about different protection circuits.. but I don't know if they'll work.. they would need testing. The 'problem' with the opamp is that it's a surface mount and if it needs to be replaced that is harder for some tech to do locally. So I was searching digikey today for a 5 V reference in through hole with I supply >20 mA. And found the LT1460 It comes in a TO-92 that can be easily replaced. Thoughts? Thanks for reading George H.

May 10, 2019 21 Replies

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Winfield Hill 7 years ago

That's been our experience. Paul once measure 100 parts from a reel (different parts, yes) and they were all very close, no outliers.

Thanks, - Win

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Gerhard Hoffmann 7 years ago

I have made similar measurements.

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and some pics to left/right. It seems, the Locky_Z curve tracer is not so intelligent at all in the DN2470 case. Maybe the Chinese - "English" - German translation has one indirection too much. The documentation is oh, s......

I wanted a depletion FET for a minimum cascode, but that was too unpredictable for my taste. So I went BJT & Zener. Zin into the source would also not have been too good.

regards, Gerhard

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