Jim said:
interestingly enough, the datasheet for a schottky BAT54 has a 5ns Trr ?!
a BAT81 is pretty good though.
And it takes substantial OpAmp slew-rate at 20MHz to get good
performance.
an LM7171 does a reasonably good job. an LM6152 is terrible. and yeah,
its the slew rate all right.
I've only used the design up to around 1MHZ.
...Jim Thompson
interestingly enough, when I go for a 200kHz bipolar sawtooth, an LM6152
is almost as good single-supply as with bipolar supplies, and is not
much worse than the LM7171. But I'll stick in a bipolar supply anyway,
it'll only cost me $0.20 or so, and this is a proof-of-concept thing
the application is a crazy smps topology that puts terrible demands on a
CT (50Hz - 250kHz BW) - so bad I havent made one work well yet. HF or LF
performance, but not both.
And the current is bipolar, so a DCCT isnt really feasible - although a
current-output (eg LEM LAH-xx) DCCT can in theory drive a schottky
bridge, in practice the phase reversals cause evil R-R glitches -
probably because when all diodes are off the impedance gets very high.
no amount of snubbing or (realistic) loading really helps. a shame
really, cos it was a nice (OK, kinda nasty) idea....
when we go to an ASIC it'll get a lot easier (it becomes the chip
designers problem
. unless we use the same french idiots who've made a
hash of the other ones. I've suggested we use a guy in Arizona, it'll
make arguments about politics that little bit more interesting
Cheers
Terry