Transistor Bias Point Detail

One of the first things you should do when you are simulating an amplifier circuit is to check the transistor operating point. If the transistor bias is incorrect, none of the other analyses will be valid. If another analysis does not make sense, check the operating point. When PSpice finds the bias point, it assumes that all capacitors are open circuits and that all inductors are short circuits. 

For a BJT, the Bias Point Detail gives the collector current, the collector-emitter voltage, and some small-signal parameters for the BJT at the bias point. For a jFET, the Bias Point Detail gives the drain current, the drain-source voltage, and some small-signal model parameters at the bias point. The results of the Bias Point Detail are contained in the output file. We will illustrate the Bias Point Detail analysis with the circuit below  

We must first set up the Bias Point simulation. Select PSpice and then New Simulation Profile from the menus  

EH EdK jflaw Pace Hiob Pgpicu Options Mfridow jjolp 

Specify a name for the new profile and click the Create button  

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Whenever you simulate an amplifier with transistors you should always check the bias point. (See Section 3.E, Transistor Bias Point Detail, on page 187.) If the bias is not correct, then the AC Sweep results are meaningless. Always check the bias point first. 

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