27. Common Emitter Amplifier (contd.) (Part B)
The chapter discusses the common emitter amplifier's small signal equivalent circuit and its parameters, such as voltage gain, input resistance, and output resistance. It also addresses the challenges faced due to the emitter resistor's presence, which stabilizes the operating point but reduces gain. Solutions include using capacitors to isolate the DC operating point from AC signals, thus restoring gain while maintaining stability.
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What we have learnt
- The gain of the common emitter amplifier is affected by the presence of emitter resistors.
- Understanding the small signal equivalent circuit is crucial for analyzing amplifier parameters.
- Using capacitors can help maintain the operating point while allowing AC signals to pass, which improves amplifier performance.
Key Concepts
- -- Voltage Gain (A)
- The ratio of output voltage to input voltage in an amplifier, typically expressed as A = -g_m × R_C/(1 + g_m × R_E).
- -- Input Resistance
- The resistance seen by a signal at the input of the amplifier, which is affected by component configurations within the circuit.
- -- Output Resistance
- The resistance looking into the output of the amplifier, which determines how much the load will influence the amplifier's operation.
- -- Emitter Resistor (R_E)
- A resistor used in the emitter circuit to help stabilize the transistor operation against beta variations, impacting the voltage gain.
- -- Coupling Capacitor
- A capacitor that allows AC signals to pass while blocking DC signals, used to isolate the AC operation of the circuit from its DC biasing configuration.
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