![]() ![]() The emitter and collector regions interchange positions in this mode. For this mode, V E should be greater than V B and V B should be greater than V C. ![]() In common emitter configuration, the output signal is 180° from the input signal. In Common Base, the output signal is in phase with the input signal. How Common Emitter amplifier differs from Common Base Amplifier?īoth the common emitter and common base configurations can be used as amplifiers. List some application of transistor when working as an amplifier: The transistor works as an amplifier when it operates in active mode with proper biasing. In characteristic response, the center portion indicates the active region. The effect of output voltage V CE on the I C is negligible for the active region. Biasing the output junction, the collector current I C increases proportionally to the base current. The BE junction is forward biased, so it acts as diode &therefore I B currents increase. When selecting the proper operating point (Q) the transistor can be used as an amplifier. In active mode, the input base emitter junction is forward biased and the output collector emitter junction is reverse biased. The transistor acts as a closed switch when a positive signal is applied to its base, turning “ON” and allowing the maximum amount of circuit current to pass through the component.The transistor becomes “OFF,” operating like an open switch, when a zero signal is applied to the base, and no collector current flows.The transistor can function as a solid state “single-pole single-throw” (SPST) switch in following case If the collector junction is larger than the emitter junction, the transistor is in reverse saturation. When switch is fully on V CE = 0 therefore I C=V CC/R L Transistor in Saturation ModeĪlso, if the emitter junction voltage is greater than the collector junction voltage, the transistor is in the forward saturation region. As a result, the transistor is turned “Fully-ON.” Here with the smallest depletion layer, the highest current flows through the transistor. It is shown in the characteristics response as a shaded region near the Y axis (I C). Now the transistor will be biased to have the highest base current applied, therefore the collector current is high for the low collector emitter voltage drop. Base emitter voltage 0.7 V (base emitter diode is Forward biased) which means input junction is forward biased. In Common Emitter transistor, V BE = V BB – I BR BĪnd V CE= βI B + V CC Characteristics of Transistor Cut-off Region of Transistorīoth the emitter base junction and the collector base junction are reversely biased in this mode. ![]() Then emitter current is represented as, I E = I B +I C ![]()
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