Hi Or put another way:
If you have a structure that uses series resistors and shunt diodes: The diodes are reverse biased when the switch is "on". The diodes are forward biassed when the switch is "off". No current when on = no noise. Bob On Mar 8, 2010, at 6:43 PM, Bruce Griffiths wrote: > life speed wrote: >> Hello Time Nuts, >> >> I'm back again. I designed bandwidth-limited (30 MHz) ADA4899-1 opamp >> circuits to buffer the 10 MHz reference, with theoretical noise of less than >> 3 nV/rtHz. Oscillator noise is about -155 dBc/rtHz from 1 KHz to 10 KHz, >> and -160 dBc/rtHz from 10 KHz to 100 KHz. Unfortunately the rest of the >> design is holding up PCB manufacture, so results on these won't be available >> for awhile. >> >> Which brings me to the other design-stopping considerations: Is anybody >> aware of low-noise analog switches that can be used to reconfigure the 10 >> MHz reference paths without significantly degrading the phase noise? As >> always, I believe 1/F noise would be the concern. Non-reflective is great, >> but I can accomplish that by using more switches and 50 ohm resistors if >> need be. Isolation is a key consideration as well. Mechanical relays are >> out of the question. >> >> An alternative to switching is phase-locking the OCXO to an external >> reference. I have thoroughly looked into this possibility, and it is likely >> my preferred approach. But I need to understand how the switching approach >> compares, hence my question. I do not need help with phase-locking; this >> feature is readily available from OCXO vendors who have dedicated years of >> research to optimizing their products. >> >> Any switch experience out there? >> >> > Why would flicker noise be a concern if there is no dc current flowing in the > switches? > > Bruce > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
