CMOS Logic gates - pull up/down? Can the gate O/P directly drive a MOSFET gate?

[Richard1234]

Hi All,

I'm looking at using some CMOS logic gates for a low-energy project (running off button cells). I'm wondering, with the CMOS gates, the NAND gates output will be hooked up to one of the AND gates inputs. Do I need a pull-down or pull-up resistor on this line? Also, will the AND gates output have enough capability to drive a IRLFL2502 MOSFET?

The NAND gate I'm looking at using is the MC74HC1G00
The AND gate I'm looking at using  is the TC7S08FU
The Transistor the AND gate's output will be on the gate of is a IRLFL2502


So:
MC74HC1G00 (NAND)   O/P ----------------------- I/P  TC7S08FU (AND) O/P ------------------------- GATE  IRLFL2502 (N CH MOSFET)

The dashed lines are where I'm asking if I need a pull-up/pull-down.

From what I can see of the datasheets, I don't think I do. Most of the stuff I've dealt with in the past has been microprocessor based. This is my first time playing with logic gates. I thought I'd check before I get some PCBs cut.

Cheers,
Richard
                       

[Zero999]

The gates you've listed all have push-pull outputs so no pull-up resistors are required.

Whether they can drive the MOSFET directly or not, depends on the switching speed. If it's just slow speed, occasional switching, then yes, otherwise a MOSFET driver is required.