Has anybody tried the AD8003 (triple video line driver amplifier) for use as distribution amplifiers? It looks to me like this part might be a decent choice.
On caveat, however: don't succumb to the temptation to reduce the circuit bandwidth by putting a capacitor across the feedback resistor- here be dragons! Each section is a current feedback opamp, intended for use in a non-inverting 2X voltage gain configuration (leading to unity gain when a back-termination resistor equal to Zo is used). It should be equally good for either 10 MHz or for PPS pulses and the like. On concern I have is that there *might* be some difficulty with driving a non- terminated transmission line (by mistake, of course). One other thing is that this part uses an "exposed paddle", which needs to be soldered down to a well-grounded pad beneath the device for both electrical and thermal reasons. For those in possession of a suitably- modified toaster oven, this should not be a big issue. Dana K8YUM On Sat, Dec 15, 2018 at 11:03 AM Anders Wallin <anders.e.e.wal...@gmail.com> wrote: > Hello Gerhard, everyone, > > I made a test using the THS3491 on a slightly modified PCB from my "FDA" > design [1]. > > At first with 200 Ohm feedback/gain resistors all I got was (pulsed, in > bursts) self-oscillation (around 150MHz or so). > The datasheet [2] does however warn about this and suggests 976 Ohms for a > gain of 2V/V, so I went with 1k. > That got rid of the self-oscillation - but now I am left with severe (16 dB > @ 230 MHz) gain-peaking! (see attached figure) > The datasheet shows a 2V/V gain-plot with only minor peaking at >700MHz. > > From past simulations [3] the gain-resistors do contribute at some point to > the noise, so increasing them further for more stability is not great for > AM or PN. > I did not bother with the phase-noise probe yet - better to get rid of that > gain-peaking first (?). > Is there anything else that can be done, besides increasing Rf/Rg for more > stability? > Anything obviously wrong with the layout? It does work fine with LMH6702 > and LMH6609. > > Thanks for any suggestions! > > Anders > > [1] https://www.ohwr.org/projects/pda-8ch-fda-8ch/wiki/wiki > [2] http://www.ti.com/lit/ds/symlink/ths3491.pdf > [3] > > http://www.anderswallin.net/2015/12/frequency-distribution-amplifier-v2-simulations/ > [image: ths.jpg] > > > On Sat, Nov 17, 2018 at 1:00 AM Gerhard Hoffmann <dk...@arcor.de> wrote: > > > > > Have you seen the new THS3491 ? LMH6702 on steroids. > > > > > > This one begs to be designed into new distribution amplifiers: > > > > Everything from DC / 1pps to a few 100 MHz into 50 Ohms, without any > > changes. > > > > (the usual gain = 2, 50R/50R out design) > > > > rise / fall 1.3 ns for 10V step > > > > slew rate 8V / ns > > > > BW 320 MHz for 10Vpp at gain of 5 > > > > Volt. noise 1.7 nV/rt Hz > > > > supply max +/- 16V, drives up to 420 mA > > > > SO-8 with thermal pad or leadless > > > > < http://www.ti.com/lit/ds/symlink/ths3491.pdf > > > > > > > regards, > > > > Gerhard > > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
