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Op. Amp. Preamplifier with mute

ACM
Prodigy 130 points
Other Parts Discussed in Thread: LM1972

Hi all,

I'm about to design a preamplifier section with an audio op. amp. (OPA2322S)

The amplifier feedback will be controlled with a digital potentiometer, I want to implement also the mute feature, could I take advantage of the op. amp. shutdown?
In shutdown mode the op. amp output will act as an open circuit, so the only way for the input signal from the input to the output is the feedback net, correct? There are other methods to achieve the mute feature without using a LM1972?

Thanks in advance

  • 0
    TI__Guru* 98965 points
    Hi ACM,

    Welcome to E2E and thank you for your interest in our products!

    You could use both devices mute/shutdown at the same time.
    When the opamp is at shutdown its output goes off so the leakage through feedback loop may go through the output stage to GND.
    Another thing you could try is to place a pull-down resistor at the output to attenuate the signal. This resistor shouldn't be too small as it will draw current during active mode.

    Best regards,
    Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Prodigy 130 points

    Hi Ivan,

    thank you for your answer, as I supposed I can't reach enough attenuation using the shutdown feature, so I will try with the LM1972.

    Regards