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SN74AUP2G04: Jittery output for 100K self bias feedback resistor

Vincent Hwang
Prodigy 60 points
Part Number: SN74AUP2G04
Other Parts Discussed in Thread: SN74LVC2GU04, SN74AUC2GU04, SN74LVC1GX04

SN74AUP2G04DRY and 100K feedback resistor between input and out pin is designed to support 38MHz 1vpp sin wave output TXCO.

SN74AUP2G04DRY is used as a clock buffer . Dc block capacitor is inserted between Txco output and inverter input

So no DC OFFSET VOLTAGE  of inverter input signal.

So, used self biased circuit

I could monitored a lot of jitter at the output of SN74AUP2G04DRY.

I used nxp 74lvc2g04 before on this location and looking for another alternative.

With NXP 74LVC2G04, I have no jitter at that same location inverter output.

Is there any reason to have jitter output with SN74AUP2G04?

  • 0
    TI__Guru* 97046 points

    Hi Vincent,

    If you need low jitter, I would recommend looking at our clocking portfolio. The logic portfolio does not specify jitter.

    Since buffered inverters have huge gain, I wouldn't be surprised at all to see jitter in this application. It sounds like you're just lucky with the Nexperia device not acting up. The SN74AUP2G04 isn't designed to operate in the linear region, just like any other buffered inverter. I would recommend to instead use an unbuffered inverter like the SN74LVC2GU04 if you're going to use feedback and a sinusoidal input.

  • 0
    Guru 316690 points

    All modern logic devices have input buffers with a small amount of hysteresis, which makes it hard to use them as linear amplifiers.

    To allow feedback, you need to use unbuffered inverters (SN74LVC2GU04 or SN74AUC2GU04).

    However, to buffer the output signal, a plain buffer is better. So you should use a device that combines an unbuffered an a buffered inverter: SN74LVC1GX04.