Subtracting 0.5V from a voltage?

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treez

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Hello,
Is the attached the lowest component cont way of subtracting a fixed 0.5V from a signal voltage?
(Schem and also LTspice sim attached)

The voltage could be anywhere between 0.5V and 5V.....and we always want to have it reduced by 0.5V
 

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Just use a simple difference amp. One opamp, 4 resistors, 1 reference (or a divider): Done.
 

For a low component count put a diode in series with your signal to subtract about 0.6V. However since your desired spec is 0.5V, try adding a potentiometer across the diode, and dial it so that results are in an acceptable range.

 

Hi,

I tend to Barry's solution, because I want it precise.

But Brad's solution is more simple.
There are two main error sources:
* drift by temperature: about -2mV/°C
* drift by output signal: Because the diode current changes with output signal voltage ... the diode voltage drop changes, too.

Klaus
 
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Here's an LTspice simulation of Barry's circuit with a TL431 reference for an accurate and stable offset.
The op amp must be a rail-rail type for operation from a single +5V supply.

 
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