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Working with bipolar analog signal with 74auc2g53

Barry Demers
Prodigy 20 points

This item supplies me with a crucial parameter, very fast rise and fall times, about 2ns worst case.  I have an ac signal that MAY be superimposed on a dc level of varying value.  I can limit the peak to < Vcc, but the signal may swing into the negative.  I am considering using a supply of +/- 1.35V to allow this to happen without damage to the device, but wonder what issues this will create.  I do realize that the digital control will need to be referenced to the negative rail.  I could run this switch with a positive supply only, and current limit the input, allowing the input signal to go negative without incurring damage, but I also need the ac component of the signal to remain intact, not severely distorted and that I'm not sure about. 

 

Any thoughts?

  • 0
    TI__Mastermind 46480 points

    You can run this either way. 

    first app,  you can tie gnd to -1.35V and Vcc to +1.35 and it will function correctly. This will not damage the part.

    second app will also work but if the ac signal goes greater than .5V below gnd then it will be clamped by the protection diode.

  • 0 in reply to Chris Cockrill
    Prodigy 20 points

    Chris Cockrill said:

    You can run this either way. 

    first app,  you can tie gnd to -1.35V and Vcc to +1.35 and it will function correctly. This will not damage the part.

    second app will also work but if the ac signal goes greater than .5V below gnd then it will be clamped by the protection diode.

     

    Thanks Chris.  I assumed that the bipolar approach was superior, just a mite messier with control signal translation.  I see the issue with the unipolar approach.  So much for linearity. 

    Based on your answer I'll move on from here.