Maker Pro
Maker Pro

why open drain vs push pull?

docb

Feb 11, 2010
131
Joined
Feb 11, 2010
Messages
131
Driving a FET/BJT with the logic output of an IC.
There are ICs with "open drain" outs, or "push pull" outs.

If I use a pull-up with the open drain, is there some benefit of that over the push pull choice, or vice versa?
 

Alec_t

Jul 7, 2015
3,215
Joined
Jul 7, 2015
Messages
3,215
Open drain allows easy OR-ing of two driver signals if required, but needs a pull-up resistor. Push-pull provides a low impedance path to both rails.
 

docb

Feb 11, 2010
131
Joined
Feb 11, 2010
Messages
131
Thanks! Sounds like just to drive a single FET, push pull is the better choice.
 

Alec_t

Jul 7, 2015
3,215
Joined
Jul 7, 2015
Messages
3,215
If you're turning the FET on only occasionally, the open drain plus pull-up resistor would be fine. It's when the FET requires high-speed switching that the push-pull driver comes into its own, to avoid the FET overheating as a result of it spending too long in the 'only-half-turned-on' state.
 
Top