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Topic: Amplifier for high speed mosfet switching (Read 574 times) previous topic - next topic

asad111

I want to drive mosfet (IRFZ44) as fast as possible using PMW. To do this, I have BD139 NPN transistor to make amplifier. A normal transistor amplifier is as follows:


Please suggest sufficient value of R1 & R2 for my application.

Do I need any additional component (diode) for PROTECTION of transistor and mosfet?

Do I need any additional component for higher speed switching?

Jiggy-Ninja

How fast? "As fast as possible" is not concrete, pick a frequency. There's problems with going too fast as well as too slow. Are we talking kHz? MHz?

There are ICs made for driving MOSFETs, they are called gate drivers. Many of them are made to have under 1 us of response time. You're better off getting some of them than trying to hack something together with descretes.
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MarkT

MOSFET gates need push-pull driver to drive them - you have to charge up the gate, and you have
to discharge the gate, both need high currents for fast switching (100mA or more is common).  Your
circuit could only turn the device off quickly, the 10k resistor isn't going to turn it on quickly.

There are literally 1000's of chips whose sole function is driving MOSFET or IGBT gates.  This is what
is used.  Since you are low-side switching a low-side driver is needed.  For instance MIC4422 will
drive almost any side of device (you can even add a gate resistor to reduce the gate current and thus
reduce EMI a bit).

Gate driver chips need _good_ decoupling, at least 1uF, must be ceramic, must be right at the chip.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

TomGeorge

Hi,
What is the load?
What is your supply voltage?

If your load is inductive you may have impedance problems as you increase PWM frequency.

Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

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