Electrons are the predominant current carriers, while holes are the lesser ones. NPN TransistorĪ Bipolar Junction Transistor (BJT) is a form of NPN transistor. There are three leads on each transistor. Transistors regulate and control the voltage between two leads to control the flow of current. These are unique in that they allow you to control the flow of current through the circuit. Electrical signals such as current and voltage are regulated, methodized, and amplified by it. Peak to Peak Voltage=67.78 mV 67.78 mV/2=33.A transistor is a semiconductor that exchanges or transfers a weak signal from a sink resistance circuit to a source resistance circuit. Sweep the Base Voltage to Get the IC=26 uA gm=1 mS Gain is approximately equal to –gmRC.The slope of the electron profile increases. The effective base width (WB) is reduced. Therefore, a DC voltage source must be replaced with a ground in small signal analysis.Įarly Effect A larger reverse bias voltage leads to a larger BC depletion region.

The small signal model is concerned only with changes in quantities.The voltage produced by a voltage source is constant.A change in VBE creates a change in base current!Įxample 4.10 Signal Generated By a microphone Small Signal Equivalent Circuit VBE=800 mV β=100 IS,Q1=3 x 10-16 A Question: If a microphone generates a 1 mV signal, how much change is observed in the collector and base current?Ī Simple Amplifier Determine the output signal level if the microphone produces a 1 mV signal. Transconductance If a signal changes the base-emitter voltage by a small amount, how much change is produced in the collector current?īut there is something else…. Large Signal Model of a BJT Called “large” signal model because this model is applicable even if VBE changes from 300 mV to 800 mV Small Signal ModelPNP Transistor Section 4.4īJT in the active region Electrons cross the forward biased BE junction and are swept reverse biased BC junction.

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