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?
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.
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.