At 12:37 AM 9/3/2007, you wrote:
Ok the Gilbert Cell is analog and the Quad Bilateral Switch seems to
be digital. And both seem to be good in both DIP and surface mount
uses for a QSD.
Not quite right, the switch has digital controls, but the switch
itself is an analog device which is used as a mixer. A sampling
integrator to be more precise.
The other day I mentioned SA612 Gilbert cells for use in a SDR not
because they are great in the IP3 area but because they are easy to
work with in a DIP package, and they are good to about 2M, and
actually have a small gain instead of a loss, so you could make an
SDR radio of modest /poor IP3 but good gain and frequency range,
something to play with. The QRP crowd has used SA612 based Qrp radios
for a lot of years and it has worked good enough, but a contest radio it's not.
I was at Radio Shack yesterday and picked up a quad comparator and
looking at its op amp like schematic I wondered if anyone has used
them and if so what might the report on them be?
Those cheap quad comparators and have very low frequency response,
not good at RF at all, and they are comparators not op-amps and can't
be used as such. The op-amp in the SoftRock needs to be low noise and
high bandwidth so that cuts out a lot of cheap op-amps, the original
used cost about $2.25 each
Dan
Cecil
K5NWA
www.softrockradio.org www.qrpradio.com
"Blessed are the cracked, for they shall let in the light."
