help!!how to drive half bridge mosfets?

[baggio2]

hi guys..i have to design a d class amplifier but i cant drive mosfets...in the first picture you see the output of comparator opamp(U4A)..it must be amplified by mosfets ..there must be a driver circuit between comparator opamp and mosfets....can anyone help to design that circuit please?

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[duffy]

Because you are using an N-channel mosfet on the high-side driver, you are going to need higher than that +15V supply to drive it... something around +25V.

It would be easier to use a P-channel mosfet for M24, something like a SUB75P03-07-E3. This has the same voltage and current rating, though a less impressive Rds on (7 milliohms). With this transistor you wouldn't need an extra power supply, though.

 

[audioguru]

The lousy old LM324 quad opamp is much too slow to be used in a class-D amplifier. Its max output is only about 2kHz when its supply is 30V.
Most other good opamps (not a 40 years old 741) have a response to 100kHz but it still isn't high enough.

 

[duffy]

Yeah, the LM324 is lousy. An LM6132 would do it, but you are going to have to add mosfet drivers because it doesn't have enough peak current.