Re: voltage keep dropping why?

alishadevochka@xxxxxxxxx wrote:
(snip)
I am also building 2nd voltage regulator.

here is the diagram
http://www.flickr.com/photo_zoom.gne?id=1075271953&size=o

I don't have 1.2v LM313 Reference Diode, but I do have 3v or 3.3v
lm133 (how do I check it?), and I am wodering if I can do something.

A single 1.5 volt chemical cell might be good enough for the negative reference, though it will get discharged when you turn the AC off, so you will have to disconnect it.

A simple, low precision 1.25 volt shunt regulator can be made by connecting two diodes in series, or by using an IR LED (like those that produce the light signal for remote controls) or by making a Vbe multiplier with any small transistor.

The last is made by connecting two approximately equal resistors in series, one collector to base and one base to emitter, so that when the voltage across the transistor rises to two diode drops, the transistor turns on and the collector current keeps the voltage from rising much higher. You need one additional resistor to the negative bias supply to feed it. Adjusting the ratio of the two resistors trims the shunt regulated voltage. None of these is as temperature stable as the integrated shunt reference regulator, but at room temperature, are probably good enough for your use.

I see that the above schematic does not show where the low current negative 10 volt bias supply comes from. Do you need help deriving that from your transformer and rectifier?
.

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