Ulrich Bangert wrote: > Bruce and Didier, > > i had the opportunity to measure the output to output as well as the > output to input isolation of a diy MAX477 based distribution amplifier > very similar to the TADD-1 (but not identical). The output to output > isolation was in the order of 75 dB while the output to input isolation > was in the order of 90 dB. This is not too bad for this simple design > and perhaps more than adequate for most of us time nuts. I have not been > able to measure the increase in terms of noise figure but this statement > must be read as: The increase in noise figure was less than the noise > floor of my equipment. Nevertheless my statement of beliefs is the same > as Bruce's one: A single transistor stage may be more easily optimized > than a multi-transistor-design. > > Best regards > Ulrich Bangert > >
Ulrich Since the MAX477 has an input noise of around 5nV/rtHz at 10MHz compared to around 1nV/rtHz for a low noise bipolar transistor, the MAX477 may be expected to be have a phase noise floor of up to 14dB higher than that of an optimised discrete transistor amplifier. This however may not be a concern unless one has an OCXO with a phase noise floor approaching the state of the art (-180dBc/Hz). There are wideband opamps with lower noise than the MAX477 available. One could always use 4 MAX 477s inparallel to lower the phase noise floor by about 6dB. Bruce _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
