PMOS pull up network?

Thread Starter

krnx2oh7

Joined Jul 17, 2011
20
I am having trouble understanding what is called a PMOS pull-up network

vin is ate the gate
the source is at the top connected to power
vd is output, vout
and a resistor goes from drain to ground below the vout

When you turn it "off" you put in vg>vth or "high"
Doesn't it not get pulled up? It goes to 0 because of the conenction to ground.

I thought pull ups and down refer to the time when no current is flowing. So w/ high gate voltage it is "off" and it is not being pulled up
 

JDT

Joined Feb 12, 2009
657
Sounds like you have the PMOS pulling the output up (when the PMOS is on), and a resistor pulling to ground (when the PMOS is off). The PMOS is switched on by connecting the gate to ground and switched off by connecting the gate to V+.

Note that in a PMOS the source is more positive than the drain. It switches on when the gate is more negative than the source. and more negative than the threshold voltage. The opposite polarity to NMOS.
 
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