AC Analysis of BJT Circuits

Difference Between Common Base Common Emitter and Common Collector: Table 6-2 compares Zi, Zo, and Av, for difference Between Common Base Common Emitter and Common Collector circuits. As already discussed, the CE circuit has high voltage gain, medium input impedance, high output impedance, and a 180° phase shift from input to output. The CC circuit has …

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Common Base Circuit Diagram: The Common Base Circuit Diagram (CB) shown in Fig. 6-34 is very similar to a CE circuit, except that the input signal is applied to the transistor emitter terminal (via C2), instead of the base. Also, there is no bypass capacitor across the RE, but the base terminal is ac grounded …

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Common Collector Circuit Analysis: In the Common Collector Circuit Analysis (CC) shown in Fig. 6-28 the external load (RL) is capacitor-coupled to the transistor emitter terminal. The circuit uses voltage divider bias to derive the transistor base voltage (VB) from the supply. The transistor collector terminal is directly connected to VCC, no collector resistor is used. …

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CE Circuit with Unbypassed Emitter Resistor: h-parameter Equivalent Circuit – When an CE Circuit with Unbypassed Emitter Resistor (RE) as shown in Fig. 6-25(a), it is also present in the ac equivalent circuit, [Fig. 6-25(b)]. RE must also be shown in the h-parameter circuit between the transistor emitter terminal and the circuit common input-output terminal, …

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Common Emitter Amplifier Circuit: Consider the Common Emitter Amplifier Circuit circuit shown in Fig. 6-17. When the capacitors are regarded as ac short-circuits, it is seen that the circuit input terminals are the transistor base and emitter, and the output terminals are the collector and the emitter. So, the emitter terminal is common to both …

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Transistor Models and Parameters: T-Equivalent Circuit – Because a transistor consists of two pn-junctions with a common centre block, it should be possible to use two pn-junction ac equivalent circuits as the Transistor Models and Parameters. Figure 6-9 shows the ac equivalent circuit for a transistor connected in common-base configuration. Resistor re represents the BE …

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AC Load Line of BJT: AC Equivalent Circuits – Capacitors behave as short-circuits to ac signals, so in the ac equivalent circuit for a transistor circuit all capacitors must be replaced with short-circuits. Power supplies also behave as ac short-circuits, because the dc supply voltage is not affected by ac signals. Also, all power supplies …

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Coupling and Bypassing Capacitors: Coupling Capacitors – To use a transistor circuit to amplify or otherwise process an ac signal, the signal source must be connected to the circuit input. If the source is directly connected to the input, as illustrated in Fig. 6-1(a), the circuit bias conditions will be altered. Figure 6-1(b) shows that …

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