System noise is the question. If the driving impedance is low, then voltage noise is more significant than current noise.
You simply can't look at the noise of the part. The key is the noise of the entire circuit. -----Original Message----- From: Bill Fuqua <[email protected]> Sender: [email protected] Date: Wed, 29 Feb 2012 10:15:21 To: Discussion of precise time and frequency measurement<[email protected]> Reply-To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] OP-Amps for 10MHz distribution...? Low noise voltage at the cost of noise current which is around 1000 times that of low noise JFETs. The discussion suggest that opamps contribute to the sideband phase noise of the signal. I am interested in the mechanism that adds this phase noise. It would have to be a small shift in either gain (changing Miller capacitance) or an internal capacitance in the opamp. I am new to this group and have some catching up to do. >I know of one op-amp that comes close to 1 nV/rtHz at 10 Hz and being >capable of useful operation as a 10 MHz distribution amplifier -- the >ADA4898 (1.2 nV/rtHz at 10 Hz, 4.3 nV/rtHz at 1 Hz). These are >wonderful parts, but the large signal frequency response with a 100 >ohm load is less than desired for a 10 MHz distribution amplifier. 73 Bill wa4lav _______________________________________________ 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.
