Lecture 3 - Lecture 3 Introduction to electronic analog circuits 1 2 Elementary Electronic Circuits with a BJT Transistor(continued Eugene Paperno

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Lecture 3: Introduction to electronic analog circuits 361-1-3661 1 2.2. Elementary single-transistor amplifiers In this lecture, we build all the possible practical circuits based on a single BJT transistor and a single resistor. (We use the resistor to translate the output current of the circuit into voltage; otherwise the circuit will not be able to provide a voltage gain.) We then analyze and compare the circuits' small-signals gains to see for what applications they can be suitable. Fig. 1 shows that only three different circuits can be based on a single transistor. This is so because the collector cannot serve as an input , and the base cannot serve as an output . The collector has a negligible effect on the base-emitter junction, which controls the injection, and, hence, the collector has a negligible effect on the current gain. The small-signal base current is much below of that in the collector and emitter, and, therefore, the voltage, current, and power gains at the base would be smaller than 1. Depending on the input-output pair, we will distinguish among three different configurations (see Fig. 2): common emitter (CE), common collector (CC), and common base (CB). In elementary circuits, the common terminal will be grounded in the small-signal analysis We will always start the analysis of a circuit from finding its static state. According to the static state, we will find the small-signal parameters of the transistor, replace the transistor by either its small-signal T or hybrid- π model, and then suppress all the static sources. We will then solve the resultant small-signal equivalent circuit in the most insightful way by applying superposition, Thévenin, Norton, and Miller theorems, and recognizing in the small-signal circuit such elementary sub-circuits as the voltage and current dividers. This will help us to better understand the circuit architecture and operation. No control Low power CE CE CB CB CC CC I n j e c t i o Extraction Fig. 1. Connecting practical signals to the transistor. v O V CC v s R C V BB v O V CC v s R E V BB v O V CC v s V EE R C CE CB CC Fig. 2. Elementary single-transistor amplifiers. 2. Elementary Electronic Circuits with a BJT Transistor (continued) © Eugene Paperno, 2008

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Lecture 3: Introduction to electronic analog circuits 361-1-3661 2 CE amplifier To define the static state of the CE amplifier (see Fig. 3), we first suppress the small-signal voltage source: v s =0.
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This note was uploaded on 01/14/2012 for the course EE 361-1-3711 taught by Professor Prof.eugenepaperno during the Fall '11 term at Ben-Gurion University.

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Lecture 3 - Lecture 3 Introduction to electronic analog circuits 1 2 Elementary Electronic Circuits with a BJT Transistor(continued Eugene Paperno

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