Re: PMOS in parallel with NMOS
- From: "robertwessel2@xxxxxxxxx" <robertwessel2@xxxxxxxxx>
- Date: Tue, 6 May 2008 21:14:57 -0700 (PDT)
On May 6, 10:52 pm, Tomás Ó hÉilidhe <t...@xxxxxxxxxxx> wrote:
Let's say I have a microcontroller pin that will have one of three
states: 5 V, 0 V or high impedence.
Let's say I have a PMOS and an NMOS, and I connect their gates
together. I connect the microcontoller pin to the gates.
Now, when my pin is high, the NMOS will turn on. When the pin is low,
the PMOS will turn on.
What will happen though when I set the pin to high impedence? I'm
hoping that neither transistor will be on, but I'm concerned that
maybe there might be some sort of voltage on the microcontroller pin
(it might be behind a large resistance, but it's still a voltage) that
will switch one of them on.
That won't work. There will be some voltage leaking from the high
impedance device, and exactly what that is, and how much current there
is, will dictate exactly what the two drive transistors are going to
do.
What are you trying to do? Build a high output tristate device? Are
you trying to drive a multi-color LED or something?
.
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