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OPA690: Question about gain.

Bhuvaneshwari K
Prodigy 190 points
Part Number: OPA690
Other Parts Discussed in Thread: OPA2690

Tool/software:

Hi, I want to use OPA2690 op amp in my circuit. I will be giving 12 inputs of 200mV each, which will be summed up to get 2.4V as output. But I want to reduce the gain such that this 2.4 output is made to 600mV. 
1) How to reduce this gain. 
2) I am using the op amp in inverting configuration. Please give me the suitable values of Rf and Ri.
3) Can it be used in gain < 1 configuration.
4) Will it be stable for gain < 1?
Attaching the circuit of reference.

  • +1
    TI__Genius 10450 points

    Hi,

    I am a little confused by the input signal you will have and the expected output. However, in theory the device should work in an attenuator configuration. The device is unity gain stable and will have a noise gain above one in this attenuator configuration, the concern comes from the values of Rf and Rg as this could affect the stability of the design. Unfortunately, I could not find additional data for this device as an attenuator so the choice of resistor values will likely take some tuning. I would start with the Rf recommended in the datasheet (402ohms) and increase Rg to get the attenuation you need. If this results in an unstable circuit, I would try reducing the Rf value and adjust Rg accordingly.

    Best Regards,

    Ignacio