Discrete Gate Driver Help!!!

defragmenter · 23rd April 2005, 12:28 AM

Hi everybody,

I am currently designing a Class BD filterless audio amplifier (8W 8ohm ) as my graduation project.

I am using 4 n-channel mosfets and also LM319 as comparators. The supplies of the bridge are +-12V's. According to my advisor, it is unnecessary to use ic gate driver for this design, this means that i have to use discrete ones. But i have no idea about discrete GD circuits. What kind of circuit do you suggest?

I have also attached the schematics.

Thanks in advance....

Bruno Putzeys · 23rd April 2005, 07:48 PM

It sounds like you can get by very well using P and N MOSFETs. A half bridge driver consists of one buffer (BC807/817 emitter follower pair), coupled to the gates through a coupling capacitor (100nF or so). From each gate to source, add zener diodes for DC restoration and dead-time setting (you can choose the zeners such that you get a DC offset so that Vth is precisely halfway the driver waveform for both FETs).

Don't forget a resistor from G to S as well to insure the whole thing doesn't blow up when you turn the power on.

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23rd April 2005, 07:48 PM	#2
Bruno Putzeys diyAudio Member Join Date: Apr 2004 Location: BE/NL/RW/ZA	It sounds like you can get by very well using P and N MOSFETs. A half bridge driver consists of one buffer (BC807/817 emitter follower pair), coupled to the gates through a coupling capacitor (100nF or so). From each gate to source, add zener diodes for DC restoration and dead-time setting (you can choose the zeners such that you get a DC offset so that Vth is precisely halfway the driver waveform for both FETs). Don't forget a resistor from G to S as well to insure the whole thing doesn't blow up when you turn the power on.

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