DC Switch

[Phideaux]

I am playing around with how to drive a relay from logic IC's (CMOS).
I've done it using a transistor (2N1104) in a common collector
configuration triggered by the IC. I would prefer to not suffer the
voltage loss of the CC configuration. I also must keep the "phase"
straight so that a high input signal generates as near as possible Vcc
to the relay. I could do it by using two transistors (common emitter
configuration) in series so the "phase" is correct and with plenty of
gain so that near Vcc is seen at the relay input. I don't know much
about Darlington's, but do know that they are two transistors in
series. I would like any ideas that anyone has on how to tackle this
problem. Thanks

 

[petrus bitbyter]

"Phideaux" <ggober@alltel.net> schreef in bericht
news:fd732a29.0403200107.8377b3@posting.google.com...

I am playing around with how to drive a relay from logic IC's (CMOS).
I've done it using a transistor (2N1104) in a common collector
configuration triggered by the IC. I would prefer to not suffer the
voltage loss of the CC configuration. I also must keep the "phase"
straight so that a high input signal generates as near as possible Vcc
to the relay. I could do it by using two transistors (common emitter
configuration) in series so the "phase" is correct and with plenty of
gain so that near Vcc is seen at the relay input. I don't know much
about Darlington's, but do know that they are two transistors in
series. I would like any ideas that anyone has on how to tackle this
problem. Thanks

You'd better look for a logic level FET. The type will mainly depend on the
current used by the relay. Some (FETs) do some tens of mA, others over 100A.
Most of the time you can drive them directly by the CMOS logic.

petrus


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