This has also been my experience. Even 5245's. Typically 1 or less volts. On Thu, Mar 24, 2011 at 10:31 AM, Greg Broburg <[email protected]> wrote:
> What is the model of the old HP counter?? Lets have a look > at the receiving end of the arrangement. In my experience > the use of an external frequency reference with HP test > boxes has been painless, not needing any extra circuitry > between the reference and the input. > > Regards; > > Greg > > > > > On 3/24/2011 6:27 AM, James Fournier wrote: > >> My intention is to divide the signal by 10 and feed it as an external >> frequency reference into my old HP counter. Hopefully this will increase >> it's stability. >> >> As for the circuits i have tried, there have been so many. Most of them >> are >> variations of each other as i experimented on a breadboard. However, a few >> examples are the inverter and diff. amp. circuits from the wenzel site. >> The >> inverter (4049) produced a small .1vpp sine wave. The amp produced another >> sine wave of of basically the same magnitude as the input. I also replaced >> the inverter with a buffer (4050) and Schmidt trigger buffer. The buffer >> produced the same result as the inverter and the Schmidt produced no >> output. >> I tried some small signal diodes, can't remember the #, to try and rectify >> the signal and just got a high output. I tried a comparator LM339 (i >> think) >> and i got no response from the output. I tried everything with and without >> an input capacitor (.1uf) and retried most of the experiments with a 10k >> pot between 5v and ground to replace the biasing resistors to allow a >> finer >> adjustment of the input. >> >> I have a feeling my problem is two fold: small signal with the forward >> voltage drop of many of the devices i have tried and the speed of the >> signal. I'm not sure everything can handle the 10Mhz signal. >> >> On Thu, Mar 24, 2011 at 7:42 AM, Bob Camp<[email protected]> wrote: >> >> Hi >>> >>> What is the resulting square wave going to be used for? >>> >>> A simple biased ACMOS gate is adequate for a lot of applications. A 0.1 >>> uf >>> cap to couple the signal to the input. A 120K to B+ and a 100K to ground >>> for >>> bias on the same input. Square wave comes out the other side. One >>> usually >>> terminates the line with 50 ohms ahead of the blocking cap. If the rest >>> of >>> your hex inverter is used for other things in the circuit, it's >>> definitely >>> the bang for the buck champion. >>> >>> That said, it's not the phase noise champion, or the highest dynamic >>> range >>> circuit in the group. Which brings us back to - what are you using it >>> for? >>> >>> Bob >>> >>> >>> On Mar 24, 2011, at 5:22 AM, Bruce Griffiths wrote: >>> >>> The attached circuit uses lower capacitance Schottky diodes than the >>>> >>> BAT45 to reduce the capacitive feedthrough so that a much smaller value >>> compensation capacitor can be used. >>> >>>> It also draws a relatively constant current from the supply and the >>>> >>> capacitive coupling between the diodes ensures that the effect of >>> transistor >>> and diode mismatch has little effect on the switching thresholds. >>> >>>> Faster switching will occur if the pnp transistor (Q2, Q3) emitter >>>> >>> current has a minimum value of a few mA whilst the diode current actually >>> goes to zero however this requires a negative supply to ensure that the >>> output signal actually switches to ground. Additional unswitched current >>> sources for the pnp transistor emitters (Q2, Q3) are also required. >>> >>>> The Wenzel circuits lacking the constant current sources have a >>>> >>> significant pulsed current flowing in the supply bypass system. >>> >>>> This can be reduced by adding an inductor in series with the emitter >>>> >>> resistor, however this has the drawback that the value of the emitter >>> resistor required depends on the input signal amplitude. >>> >>>> >>>> Bruce >>>> >>>> Charles P. Steinmetz wrote: >>>> >>>>> One problem that is evident when a simple longtailed pair (differential >>>>>> >>>>> amplifier) is used to convert a sine wave to a square wave is the tilt >>> that >>> is evident in the waveform when the output transistor is conducting. This >>> is >>> due to feedthrough from the input signal via the emitter base capacitance >>> of >>> the input transistor to the emitter of the output transistor. >>> >>>> The attached circuit schematic illustrates one classical method of >>>>>> >>>>> minimising this tilt. >>> >>>> Compensation isn't perfect due to the voltage dependence of the emitter >>>>>> >>>>> base capacitance but the tilt can be significantly reduced, >>> >>>> I have used the attached circuit, which is a bit simpler, to the same >>>>> >>>> end. For the reason you stated, the compensation is not perfect, but it >>> is >>> surprisingly good. The compensation slows the rise and fall times by >>> about >>> 1 nS, from about 7.5 nS to about 8.5 nS. >>> >>>> This circuit produces 5 Vpp output -- for 3.3 Vpp output, using a 121 >>>>> >>>> ohm tail resistor should work. >>> >>>> Best regards, >>>>> >>>>> Charles >>>>> >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> 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. >>>>> >>>> <EnhancedLTPShaper2.PNG>_______________________________________________ >>>> 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. >>> >>> >> >> > > _______________________________________________ > 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.
