Drive a Power MOSFET from a LOGIC LEVEL

[kkdelabaca]

Hello,

I have a POWER MOSFET, concretely the reference IRLR024:
http://www.irf.com/product-info/datasheets/data/irlr024.pdf

The question is: I can connect the output of a logic '74HC' or '74LS' directly to the Gate of the MOSFET? Or I need some pasive components?

The datasheet put: "Logic-Level Gate Drive"

Regards!

 

[LLxios]

the best thing to do is to place a resistot between the gate and the source. value is not so importend, but 100K is good

 

[platonas]

Hi,
I don't agree with LLxios in the value of the resistor.
The resistor must be small in order to charge as quickly as possible the gate of the mosfet. A resistor of few ohms to some KiloOhms is recommended depending on the power the mosfet should handle in your application.
For large mosfet currents and high frequencies you need a smaller resistor, for lower currents and/or low frequencies a resistor of some KiloOhms is ok.

If you drive the mosfet directly, it is usualy fine but in case of a mosfet failure, you might destroy the driving logic IC.
Regards
P.

 

[Kral]

kkdelabaca,
This will work if turn-on/turn-off times of the MOSFET are not critical. To turn the MOSFET on quickly, you need much more drive current than an ordinary logic gate can provide. Also, if other logic devices are connected to the gate that is driving the MOSFET, the input capacitance of the MOSFET will affect the rise/fall times of the logic signal. In cases like this, an isolation resistor will prevent the MOSFET input capacitance from affecting the ligic rise/fall times. However, the turn-on/turn-off times of the MOSFET will be even worse because of the RC time constant formed by the isolation resistor and the MOSFET input capacitance. There is no free lunch!
Regards,
Kral

 

[umup]

LLxios Gate-Source resistor neded only when driving output can go to Z-state, if not, its not needed
platonas You talking about series gate resistor, not Gate-Source resistor. '74HC' logic don't have enough powerful output to busy about MOSFET's Gate protection from output current, so series resistor not needed

 

[siongboon]

For MOSFET, maybe the resistor is not necesaary.
I am not sure.

Try using 1kohm between the logic and the gate input.
Reduce the resistence low enough to switch on the transistor.

Higher resistence might reduces the response time or speed.
Lower resistence need more power.

Here's some references for you.
General schematic for connection with most transistor.

**broken link removed**