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precision fixed voltage source for summing op amp? use LM317?

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danjel

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I want to shift an input voltage of the range -5V to +5V into the range 0 to +10V.

My plan is to feed the input into a two input inverting summing op amp. The other input will be fed +5V so that the other voltage is always shifted up into the desired range.

My question is what is the best source for a precise 5V? Should I use an LM317?
 
You need an op-amp and a regulated power supply or voltage reference.

Here's a tutorial.

**broken link removed**
 
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Thanks I looked at that tutorial before but the example fails if you input the values I used.

e.g.

Input signal ranges from -5 to +5V, scaled to range 0-10V
V1 = -5V
V2 = 5V
Va = 0V
Vb = 10V

G = (10-0)/(5-(-5)) = 1
Vy = 0-1(-5) = 5
Vt = 5/1-1 = 5/0 DIVIDE BY ZERO NOT POSSIBLE

However if I use an inverting summer with two inputs and gain of 1 it is easy:
input 1 is the +/-5V signal. Input 2 is the 5V reference voltage (which is really what my question is about. If I used voltage divider it is not accurate enough)
Output of this summer can then be inverted with another opamp stage.

So again my question is: what should I use as the voltage reference?


p.s. My power supply is a regulated +/-12V. I also want to use as few components as possible.... should I just use precise resistors as voltage dividers???
 
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I think you're right about the amplifier, I'll check tomorrow.

I've used the LM4040 before, it's very good, better than the TL431 which is more common.

EDIT:
It does have the disadvantage of not being adjustable but that doesn't matter here.
 
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