Electronic – Voltage follower with shift

level-shiftingoperational-amplifiervoltage

I am trying to figure out a simple application/ circuit that would allow me to shift the voltage a little bit. Lets say we have an input voltage of range from 0 to 1 V. I need an output voltage of 0.2 to 1.2 V. This is just an example but I am looking for a generic solution. There is no negative voltage available in the circuit.

Best Answer

The classic 4-resistor difference amplifier will do what you want:

schematic

simulate this circuit – Schematic created using CircuitLab

This circuit keeps the difference between Vout and Vref equal to the difference between V+ and V-, effectively adding Vref to V+ if V- is grounded.

The opamp tries to keep its two input terminals at the same potential using negative feedback:

$$ \frac{V_{out} + V_-}{2} = \frac{V_{ref} + V_+}{2}$$

Multiply both sides by 2 and rearrange the terms to get:

$$V_{out} - V_{ref} = V_+ - V_-$$

simulation result