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Analog Engineers Calculator

Hello ALL,

I am looking for a voltage level shifter which shifts (+1.5V to -1.5V AC signal) to (0 to +3V AC signal) for giving it to a micro-controller analog pins. I selected a simple Inverting voltage summer as shown below which serves the purpose. 

But, the TI's Analog Engineers calculator recommends another circuit where it asks the reference voltage to be inserted which is a non-standard value to be given at +ve pin of opamp. 

I would like to know whether I can go with the circuit I selected or Is there any strong rationale to use the TI recommended circuit.

  • Hi Rajesh,

    The Vref voltage can be created using a voltage divider and the supply voltage of the op amp. For example, if you have a 5V supply for the op amp, divide down the 5V to give you 0.65V.

    Thank you,

    Tim Claycomb

  • Hi Tim,

    Thank you for your reply.

    I'd like to know the advantage of the TI Analog Engineer's Calculator recommended circuit to the classical circuit I mentioned in the original question.

  • Hi Rajesh,

    The main difference is that there is a reference voltage to bias up the output voltage in the TI Analog Engineer's Calculator. Without a bias voltage the output will not be able to swing from 0V to 3V.

    It also appears that the classical circuit is more of a summing amplifier with V1, V2, and V3 as input voltages whereas the TI circuit is a level shifting circuit.

    Thank you,

    Tim Claycomb