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SN74AUP2G04 for colpitts oscillator

Yan Drolet
Prodigy 90 points
Other Parts Discussed in Thread: SN74LVC2GU04, SN74LVC1GX04, LMV321

Hello,

I'm using the SN74AUP2G04DSFR to create a colpitts oscillator. Everything is working great. In order to qualify the part for production, i would like to have the following informations that are not specified in the datasheet.

1 - I notice that i don't need to add a bias resistor for the oscillator to work. This means that there must already be a bias included in the chip. What is the value of the bias resistor (from input pin to output pin) and is it guaranty that there will always be one ?

2 - What is the minimal gain when used in the linear region ?

Thanks

Yan

  • 0
    TI__Guru 55960 points
    Hi Yan ,

    There is no bias resistor used from input to output as I know . This is not generally to be used in the linear region of operation but is used in digital logic switching 0 /1 . you would be better if an opamp is used as configurable gain can be set by the feedback resistors.
  • 0 in reply to ShreyasRao
    Prodigy 90 points
    Choosing an op-amp is not an option, package are too big and more costly.

    I understand that it is normally used in digital world, but the transistor inside the chip always have a linear region witch i'm trying to get more information on.

    Thanks for the information on the bias.

    Can you still provide gain data on the CMOS input ?

    Thanks

    Yan
  • 0 in reply to Yan Drolet
    Guru 242810 points
    Individual transistors may have a linear region, but this is visible to the outside only when neither the input nor the output are buffered with additional transistors. Devices in the CMOS ("C") logic family had such a simple design, but this is no longer true for any family sold nowadays.

    Additionally, modern families such as AUP have input hysteresis (even if it's smaller than for 'real' Schmitt-trigger devices), so there is no linear region. For practical purposes, assume that the gain is nearly infinite.
  • 0 in reply to Clemens Ladisch
    Prodigy 90 points

    This is very useful information, thanks.

    Would you than recommend using SN74LVC2GU04 for this application ?

    I could also use SN74LVC1GX04, but the package is too big for our actual design.

    Thanks

    Yan

  • 0 in reply to Yan Drolet
    TI__Guru 55960 points
    Hi Yan ,

    LMV321 is available in DCK package .
    LM358DGK costs less than AUP2G04 but will be 5V or higher operation . What is the frequency of operation ?
  • 0 in reply to ShreyasRao
    Prodigy 90 points

    We currently use a DSF package (1mmx1mm). We will have to make some place for YZP. DCK is definitively too big.

    Frequency is around 15MHz. Cost must include all component, not just the package. All op-amp also adds complexity and surrounding parts.

    Would you recommend using SN74LVC2GU04 for this application ?

    Thanks

    Yan