driving an FET using PWM?

[disenteako]

pwm fet

Hi! I have a project which consists of a buck converter that needs to drive an NMOS or a PMOS using a PWM output from a microcontroller. The problem is the PWM output of the microcontroller has a 0V to 5V range which is not enough to properly turn on and off the FET given a FET Vin of 16V-20V. What FET driver or FET gate driver can you suggest to solve my problem? Thanks.

 

[mister_rf]

fet pwm

Read here:

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http://focus.ti.com/lit/ml/slub005a/slub005a.pdf
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http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1142,C1041,P8290,D5777

 

[disenteako]

driving fet

Very nice. Thank you very much!!! : )

 

[disenteako]

driving a fet

Follow up...

I'm having trouble making my buck converter work. I've already used this

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After computing the inductor and capacitor values, I still can't get a decent output on my circuit using Multisim.

Basically, I just want to output 12 Volts given an input voltage of 20 Volts using a MOSFET in a buck converter. My FET works properly but the Voltage output after the inductor and capacitor values aren't. Any suggestions?

 

[Mr.Cool]

multisim pwm

posting a schematic might help..

but did you put a load resistor in parallel with your output capacitor? sometimes you need to pull a little current to get the thing working right. pick value based on simple equation:

R = Vout/Iout

make sure your current is appropriate for the size of your converter.

Mr.Cool