Solid State Relays come in two forms (as far as I know) - there
are units using a BiPolar transistor as a switch, and others which
use a FET as a switch.  Both are optically coupled - a photoisolator
activated by a low voltage/low current signal (5v @ 15mA) drives the=20
switch device. The bipolar devices are intended for DC and the FET
devices are often intended for AC loads.

These devices are intended for switching power loads - usually 60/150=20
volts at anything up to several Amps. They usually include reverse=20
voltage and spike/surge protection, so they tend to be rather expensive.
Also, they are not intended for low level signal switching.

This is general information - I do not know exactly what configuration=20
the Jameco devices use.

The MAXIM analog switches are just about the best units I have found
for switching low-level signals - I have used them for many years in
lots of different projects.

Roy J. Gromlich

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