On Tue, 03 Jan 2012 07:01:13 +0100, ehydra <[email protected]> wrote: >David schrieb: >> I could analyze it on SPICE but I suspect the real world construction >> parasitics will be what limits the performance. I just sketched it >> out in my notebook but I will see if I can post it somewhere. Is >> there a quick and dirty online schematic capture site? > >Scan it. I will make a LTspice file. > >> >> It is not that complicated being a differential amplifier driving >> complementary pair of emitter followers, a pair of voltage clamps, and >> then a pair of complementary current mirrors configured as >> transconductance amplifiers. > >I want to SEE it including all circuit parameters. Thank you.
I am entering it into LT Spice for practice. I will post the results and files here when done. I need to rethink the level shift configuration. >> When you say symmetry limiting do you mean to prevent second harmonic >> distortion like for driving a mixer? I was thinking of this more for >> driving a single ended transmission line cleanly while maximizing the >> edge rates and minimizing jitter. Duty cycle correction could be >> added pretty easily. > >Hm. I think second harmonic distortion looks very much like intentional >symmetric waveform in the first instance. The fun begins if we decide to >look for equal time distance or equal power for both phases. Interesting. > >> >> The circuit you linked is going to have a little problem since both >> the 2N5769 and the 2N5770 are NPN and the circuit requires a pair of >> PNPs. Other than that it looks perfect for driving a high level >> mixer. > >As far as I know driving a mixer was the circuit intention. I SPICEd it >with BFR93 types. The circuit has a high reflection coefficient, >unfortunately. Maybe this is unavoidable and we need a diplexer. The output is low impedance, unmatched, and I suspect not quite symmetrical so I would expect this. Does it matter though if the mixer is close by? >Yes, looks like an typo for having 4 NPNs there. I will clarify this >with Chris Trask. Thanks. Unfortunately, RF PNP transistors tend to be rare or expensive so when I saw that schematic my first thought was, "Hmm. I wonder if that is the RF PNP I have been looking for. I did not know the 2N5770 had a PNP complement. Wait a sec . . ." I have been considering the PNP BFG21 and NPN BFG97 made by NXP. They are SOT-223 so should be easier to prototype with than a smaller package. The On Semiconductor TO-92 NPN MPSH10 and PNP MPSH81 would be good also but the later is being discontinued. _______________________________________________ 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.
