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Non_inverting Amplifier using AD711

i am trying to learn non-inverting amplifier design using AD711. I have designed a circuit and tried to simulate using LTSpice. When the opamp is supplied with +/- 5V, it works as expected. but when i supply 5V and GND to opamp, it's not working as expected.

I have attached both circuits for reference. Basically the vref will be 0.3V and gain is 2.

So in working model, i get 0.6V as output which expected whereas in non-working model i get 1.17V which does not make any sense to me.

Can please some one explain why it is?


  • You have two problems with what you are attempting to do.

    First, if you read the AD711 datasheet it specifies on Page 2  the minimum power supply as +/- 4.5V or 9 V total between -Vs and +Vs. You have only 5V. Sometimes the Spice models for an amplifier will "work" below the specified minimum supply but it might not.

    Second, This might not be causing your problem but in the Dual +/5V version you have R1 and R3 connected to ground which is mid way between the -5 V and +5 V supplies. In the single +5 V supply version you have R1 and R3 still connected to ground which is now -Vs of the op-amp. What I think you really wanted to do is connect R1 and R3 to another voltage source which is mid way between the voltages applied to -Vs and +Vs, which is now +2.5V. This is a common mistake made when converting a dual supply voltage circuit to a single supply circuit.

  • Thanks for the response. Modified the circuits based on your suggestion. everything works as expected.

    Key take way is study the datasheet if something is not working.

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