Hi ..... and thus if you drive it from a low impedance node you can get pretty good isolation.
Bob On Feb 19, 2010, at 5:59 PM, Bruce Griffiths wrote: > life speed wrote: >> Message: 6 >> From: Pete Rawson<[email protected]> >> Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution >> >> >>> Clay, >>> >>> Analog devices AD4899-1 voltage noise = 2nV/rtHz @ 10Hz; GBW = 300MHz. >>> >>> Pete Rawson >>> >> That is an interesting part. >> >> So, how does one think about reverse isolation in a feedback amp? Is the >> open-loop gain of the amp applied to the spurious signal to cancel it? The >> spurious, reduced by the ratio of the 50 ohm source impedance, to the output >> impedance of 0.7 ohms of the amp (-18 dB) appears at the inverting input . . >> . >> >> And what would appear at the non-inverting input? >> >> Off to the simulator. >> >> Clay >> >> > Reverse isolation is highest if one uses a non inverting amplifier rather > than an inverting one. > The signal at the inverting input is coupled to the non inverting input via > the differential input impedance (predominately capacitive) of the opamp. > ie finite input stage current gain and emitter base (along with package > strays) capacitances are the principal contributors at least for frequencies > where the input stage output voltage swing is small. > > Bruce > > > _______________________________________________ > 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.
