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ADG904

I have a technical question on ADG904 RF switch.

We wish to use it as analog switch for single frequency clipped sine-wave TCXO selection (from 10MHz to 100MHz).

The problem is that we can’t load the TCXO for more than 10pF + 10K ohm and therefore we can’t load the switch output by 50 Ohm, only 10K (resistive)/10pF or more (actually it goes to another chip with high impedance input).

The question is – can we use this switch with high impedance output instead the regular usage as RF switch with 50 Ohm output?

Note: No use of wide band signal, only single frequency clock.

Data sheet link: http://www.analog.com/static/imported-files/data_sheets/ADG904_904R.pdf

Thanks

  • Hi FreddyS,

    I think there are a few things to consider here in this crystal switching application.  It sounds like your shunt load conditions for the TCXO are up to 10pF-10kohm (in parallel) followed by a high impedance input IC.  If my assumption is wrong let me know.  In the high impedance IC termination case the ADG904 switch will have an attenuating effect on your sine-wave signal.  Added in some large value series resistors to the switch should help e.g. 10k+. 

    Regards,

    Eric.