SN74LVC1G32: 74LVC1G32 drives MOSFET LED driver

Vidhya J

Intellectual 365 points

Part Number: SN74LVC1G32

Tool/software:

Hi Team,

Output of Logic gates can be used to drive N-MOSFET gate of LED circuit?

OR can NPN BJT be used ?

What is the advantage?

Regards,

Vidhya

6 months ago

0 Clemens Ladisch 6 months ago

Guru 283470 points

That depends on the capacitance of the gate. Logic devices can be connected directly for up to about 70 pF; for larger gates, you need a current-limiting resistor (the LVC absolute maximum rating is 50 mA).

+1 Vidhya J 6 months ago in reply to Clemens Ladisch

Intellectual 365 points

HI Clemens,

The input capacitance of BSS138 NMOS is 50pF max.

So the LVC output can be directly connected to gate of BSS138 NMOS without series resistor?

Thanks,

Vidhya

+1 Clemens Ladisch 6 months ago in reply to Vidhya J

Guru 283470 points

Yes; such small MOSFETs can be driven directly.

You also asked about BJTs. You can use them; then you have to size the base resistor correctly (large enough so that the LVC output can drive the base current; small enough so that it can drive the BJT into saturation).

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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SN74LVC1G32: 74LVC1G32 drives MOSFET LED driver