Hi , I have a voltage source it can be a sensor or smth , I need to add some constant offset to that votlage.
I dont want to use many transistors and keep the power consuption minimum.
For example ,

SOURCE	OUTPUT
100mV	90mV
1V	0.990V

 

This is easy to do with one small opamp. What is the highest frequency component of the input signal? What power sources are available for the circuit?

Also, what is the output of this circuit driving downstream? Any specific output or input impedances?

ak

 

The transistor CE drop is pretty constant for relatively wide range of Ic currents:



You can try to place a bjt is series to drop the voltage. By changing the base resistor (10k) you can vary this drop. Don’t forget the base current flows to emitter also:

 

I need to add some constant offset to that votlage.

How stable does this offset voltage need to be with temperature?
Do you need to vary it with a pot?

 

What supply voltages are available?

 

IF the sensor output feeds a high impedance input, the simply putting a simple negative voltage source in series can be the solution. Get one of those "dip format" voltage converters that provides an iaolated output of 5 volts or less, and use a resistive divider to provide that ten millivolts across the one resistor. Then put that isolated voltage in series to subtract from thesensor voltage. Only 3 components, and two of them are resistors.. YES, it does require 5 volts and a return connection.