Hi Unless you really beat on the thing for days on end, you can do without the 330 ohm and 100 ohm resistors (along with the two diodes). Most modern gates have pretty robust protection diodes. The source impedance is high enough after the transform that the available current is pretty low. On a NC7SZ125 the negative diode is rated for 50 ma max and the positive diode is rated for 20 ma
Some math: If the two 1K’s properly terminate the circuit, you have a 250 ohm source. (500 ohm load and 500 ohm transformed from the sine input). A 1V overdrive (1/2 V + and 1/2 V -) will put 2 ma into the diodes on the peaks. The more likely case is that the negative is hit a bit harder. The bias is most likely a bit below 1/2 Vcc for best symmetry. None of this is to say you *should* hit the diodes. No matter what sort they are, the performance will degrade a bit when you do. How much is of course a “that depends”. Most of us are not driving the gate with a -180 dbc/Hz source and expecting -177 out of the gate. Bob > On Jan 19, 2018, at 8:14 PM, Bruce Griffiths <[email protected]> > wrote: > > Something like the attached circuit is suitable for driving the MCU clock > input directly. > The diodes should be schottky signal diodes like the 1N5711 series. The > series resistors limit the diode peak current and the CLK input protection > network current. It should work with inputs from 1V pp to 8Vpp. If SMT > components were used it should all fit on a DIP compatible daughter board. > > Bruce >> On 20 January 2018 at 12:37 Bob kb8tq <[email protected]> wrote: >> >> >> Bob >> >> With a 1V p-p sort of output, a simple matching network will get you into >> the 4 to 6V p-p range. >> Drive that into a 5V compatible CMOS gate and move on …. If you have a super >> hot output, put >> a 3 db pad on it. >> >> Bob >> >>> On Jan 19, 2018, at 5:40 PM, Tom Van Baak <[email protected]> wrote: >>> >>>> Tom >>>> What's the input signal amplitude? >>>> What's the desired output signal (eg 5V CMOS, 3.3V CMOS etc)? >>>> Bruce >>> >>> It's for a typical 5 or 10 MHz OCXO / Rb / Cs with sinewave output; say, 1 >>> Vpp. The output should be 3.3 or 5 V depending on what the MCU needs. It >>> doesn't have to have stunning performance: think breadboard, PIC, Arduino >>> sort of stuff. I was looking for something in a PDIP-8 package; the same as >>> all the picDIV or picPET chips I use. That's why older parts like µA9637 / >>> DS9637 came to mind. >>> >>> /tvb >>> >>> _______________________________________________ >>> 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. > <PIC_CLK_Network.gif> _______________________________________________ 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.
