Practical Electronics/Amplifiers/Common emitter

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Transistor - Common_Emitter_amplifier[edit]

Common Emitter Amplifier

Common emitter amplifier.svg


  • Current Gain: ..... HIGH
  • Voltage Gain: ..... HIGH
  • Power Gain: ..... HIGH
  • Input Impedance: ... AVERAGE
  • Output Impedance:... AVERAGE


Input Resistance(base): Zb=β×re'

-> 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.