-> β: Current Gain (Ic/Ib), where 'Ic' is Colector DC current and 'Ib' is DC Base current;
-> re': Base-Emitter (Ut/Ie), where Ut is thermal voltage(≈25mV at 25°C) and
'Ie' is DC emitter current;
Input Resistance(general): Zg= Zb || R1 || R2, where R1 and R2 are the same as the picture above.