Subject: Re: How do I feed 0v/1v logic levels to CMOS?
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Date: Sat, 12 Oct 2002 17:54:11 +0100
NNTP-Posting-Date: Sat, 12 Oct 2002 16:54:14 GMT
Thanks everyone for your advice, it gets me off to a great start!
One point I was wondering about is battery power conservation. The temp monitor
is permanently supplied by a single AA 1.5v battery but draws an insignificant
current. If I feed the 2 outputs (temp too high signal & temp too low signal),
one of which will probably be high, thru my circuit I don't want to drain too
much current which will reduce battery life. That's why I was considering MOSFET
input op-amp like the CA3130E instead of discrete components like transistors
etc, am I on the right with this assumption?
Also the circuit am I building will only the on while the PC is on, whilst the
temp monitor will always be on. I read somewhere that's it's not a good idea to
feed a signal to CMOS without a power supply. Would this be a problem or not
relevant for such a low voltage?
If anyone is interested I'm building a circuit to control the PC cooling fans by
monitoring the temp inside the case.
Thanks again, people.
On Sat, 12 Oct 2002 12:53:44 +0100, Miles wrote:
>Can anyone please help me with (I hope) a simple problem.
>I have a temperature monitoring device with 1.5v battery supply. It outputs
>logic levels of 0v (low) and 1.5v (high).
>I want to connect this to a CMOS circuit I'm constructing running of 0v-12v
>supply (on a PC). The CMOS circuit is a simple logic one using 4001 type chips,
>I know I need some kind of voltage shifter to up the high level to at least 5v
>or so. I'm considering using single-supply op-amp as a voltage comparator.
>Can anyone suggest a simple way of doing this? Any help, references, sources
>would be very much appreciated.