I need to generate 0-15V output PWM singal ( max out put current is 4.5 mA only), using micro controller PWM feature. I observe one Design by using Two Transistor(PIC 1) ,I don't why two transistor needed for this , I think this can be done by sigle transistor only (PIC1). Tansistor used is MMBT2222A NPN.
Q1) One reason I can think , to keep same polarity of both input and output signal, but does it matter if some load need PWM input to drive it.
Q2) R1, R3 and R7 is to protect transistor from floating base condition , Correct me if i ma worng.