Your redrawn circuit will not work:
1) The upper P-channel Mosfets will never turn off.
2) The lower N-channel Mosfets will barely turn on.
3) The gates of all the Mosfets will burn out with almost 24V on them.

I cannot read the part numbers of the Mosfets so they might need a Vgs of 10v to turn on. Your emitter-followers will have an output of 0.3V to 4.3V.

 

Your redrawn circuit will not work:
1) The upper P-channel Mosfets will never turn off.
2) The lower N-channel Mosfets will barely turn on.
3) The gates of all the Mosfets will burn out with almost 24V on them.

I cannot read the part numbers of the Mosfets so they might need a Vgs of 10v to turn on. Your emitter-followers will have an output of 0.3V to 4.3V.

They are irf9z24n and irfz24n vgs of 4V is reqd.

 

I would suggest using dedicated off-the-shelf FET bridge driver ICs, such as the IR2110 or its brothers, particularly if you want to switch FETs at high frequency. A problem with your present circuit is that at 100kHz it likely won't be able to handle enough current (~1A or so) to charge/discharge the FET gate capacitances sufficiently fast to prevent over-heating. Your circuit also provides no dead-time to prevent shoot-through by ensuring that the top and bottom FETs never conduct simultaneously during there finite switch-over times.

Thank you for your reply. I'll try and implement the circuit using IR2110.

 

My H-bridge circuit properly uses complementary NPN/PNP 2N3904/2N3906 emitter followers to drive the Mosfets:

What are your voltages??

 

The voltages powering the complementary driver transistors and the Mosfets are no higher than 20V, because most ordinary Mosfets turn on well with a gate voltage of 10V but 20V is the maximum allowed gate voltage.

 

The voltages powering the complementary driver transistors and the Mosfets are no higher than 20V, because most ordinary Mosfets turn on well with a gate voltage of 10V but 20V is the maximum allowed gate voltage.

Thank you so much.....I'm grateful for your reply. I'm using 24 V...Won't work would it?

 

+24V is too high for the Mosfet gates.
Do it like this:

 

+24V is too high for the Mosfet gates.
Do it like this:

Thank you, I'll try it with 18V... Is the extra 2N3904 in series with 1k resistor for the other half for dead time??

 

Is the extra 2N3904 in series with 1k resistor for the other half for dead time??

No. It provides phase reversal.

 

No. It provides phase reversal.

I tried just one leg ie. one p channel mosfet and one n channel.. The p-channel is still getting hot. no load. The emitter output is working fine...

 

I tried just one leg ie. one p channel mosfet and one n channel.. The p-channel is still getting hot. no load. The emitter output is working fine...

The push-pull Mosfets cannot get hot with no load. One is completely turned off with no current and one is completely turned on with no voltage.

 

The push-pull Mosfets cannot get hot with no load. One is completely turned off with no current and one is completely turned on with no voltage.

Thats right. I'm using irf9z24n and irfz24n.would that make a difference.

 

Are you sure you haven't got the P-FET source and drain reversed ? Source goes to +V.

 

Are you sure you haven't got the P-FET source and drain reversed ? Source goes to +V.

I checked, the drain is connected to drain. Will changing the resistor of 22ohm make a difference

 

I checked, the drain is connected to drain. Will changing the resistor of 22ohm make a difference

The supply is getting loaded dropping from 18V to 12V and voltage at Drain o/p is approx. 4V.

 

Perhaps your P-FET is damaged from being driven with 24V previously?

 

Perhaps your P-FET is damaged from being driven with 24V previously?

New pcs were connected... MOSFETs look ok on Multimeter.

 

New pcs were connected... MOSFETs look ok on Multimeter.

Will 7818 regulator suffice for the above circuit??

 

A 7818 will be fine if it has an input of at least +20V and it has near it the input and output capacitors shown on its datasheet.

I show half of the H-Bridge and voltages that should happen when the input is 0V and with +5V.
Please list any parts changes and measure your voltages.

 

A 7818 will be fine if it has an input of at least +20V and it has near it the input and output capacitors shown on its datasheet.

I show half of the H-Bridge and voltages that should happen when the input is 0V and with +5V.
Please list any parts changes and measure your voltages.

The output at R1 is showing 8.5v on dc voltage on Multimeter. On cro shows square wave 18.4vmax. P MOSFETs however is getting hot and vout dc voltage on Multimeter shows approx. 4V. All parts are the same.

A 7818 will be fine if it has an input of at least +20V and it has near it the input and output capacitors shown on its datasheet.

I show half of the H-Bridge and voltages that should happen when the input is 0V and with +5V.
Please list any parts changes and measure your voltages.

Vout is voltage at the drain