Hi The gotcha with simulating low noise buffers is the lack of a good non-linear model to include the up conversion of audio noise. All (practical) buffers exhibit this phenomenon. Since all amps have audio noise and all have up conversion, it is always present. It is responsible for the well know “rise from floor” that is seen on all buffer amps. That makes this a very much “build it and see” sort of thing. After you have measured data, an empirical model can be created that will allow the simulation to match the measurement.
Bob > On Dec 27, 2015, at 9:25 AM, Anders Wallin <anders.e.e.wal...@gmail.com> > wrote: > > Hi all, > Based on the response to my distribution amplifier prototype&measurements I > ran a few SPICE simulations with the old AD8055 design and an improved > design. > > The changes are: > - better op-amp > - improved DC-bias "T" circuit > - lower resistance values (esp. gain-setting resistors) > > results & discussion in my blog: > http://www.anderswallin.net/2015/12/frequency-distribution-amplifier-v2-simulations/ > > The simulations would indicate a 12 to 13 dB improvement in noise floor is > possible. I could not find a good ADA4899-1 spice model. One has realistic > AC gain response but unrealistic 1/f noise. The other model I found has a > realistic 1/f noise but infinite AC gain bandwidth :( > > again suggestions are welcome, I'll probably order boards and parts for the > next prototype in a few days. > > I will look at Bruce's suggestion for the BNX002 (SMD equivalent > available?) on the powersupply. There is already a common-mode choke (TDK > ZJYS) and an NFE61P before the regulator, as well as ferrites before the > bypass-caps and vcc-pin of each output amplifier. > > thanks! > Anders > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
