I did not have any experience with BJT so I am having a hard time to analyze the circuit. From research, I know Q1 is common base and Q2 and Q3 are common emitter. To draw the small signal model, I would have to short all DC source and capacitors.
I am not sure what to do next. I tried to break the circuit into 3 parts to analyze but I am not sure what to do with the 47K, 56K,15K resistors that's connected to Q1.
Can anyone help with the small signal analysis?
To find the input impedance, applying KCL then it would be 12/47k + gmVpi + Vpi/rpi + Vin/10K?
I am a bit confused with Vpi and rpi. Do I need to calculate that or it's from the BC547 data sheet?