This is a 12V dc motor speed control cicuit with forward and reverse function(cw and ccw). Not complete though. It functin like this , upper two 324 operational amplifiers make a triangle wave generator. Lower left 1/4 lm324 compares triagle wave with input set point and hence outputs pulse...
Let me explain. Attached is a typical chinese inverter output stage. A full hbridge stage. So hi side driver is needed. But instead using costy driver ics it can be done with discrete components like a diode ,capacitor transistor. Action is the same. Initialy when low side fets are on V2 ,12V...