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Large-Signal dc Analysis Procedure: (1) select the operation mode of the BJT (2) use selected model for the device to solve the circuit and determine IC, IB, VBE, and VCE (3) check to see if the solution satisfies the constrains for the region, if so the analysis is done (4) if not, assume operation in a different region and repeat until a valid solution is found This procedure is very important in the analysis and design of the bias circuit for BJT amplifier. Large-Signal dc Analysis:characteristics of an npn BJT Large-Signal dc Analysis:Cutoff-Region Model VCB reverse bias ? VBE reverse bias ? If small forward-bias voltage of up to about 0.5 V are applied, the currents are often negligible and we use the cutoff-region model. Large-Signal dc Analysis:Saturation-Region Model VCB forward bias ? VBE forward bias ? Large-Signal dc Analysis:Active-Region Model Important: a current-controlled current source models the dependence of the collector current on the base current VCB reverse bias ? VBE forward bias ? The constrains for IB and VCE must be satisfy to keep BJT in the active-mode

Amplifiers Chapter 13: Bipolar Junction TransistorsĬircuit with BJTs Our approach: Operating point - dc operating point Analysis of the signals - the signals to be amplified Circuit is divided into: model for large-signal dc analysis of BJT circuit bias circuits for BJT amplifier small-signal models used to analyze circuits for signals being amplified Remember !.Bipolar Junction Transistor Circuit Analysis EE314