Using PSpice to check your calculations BJTs

Example

Forward Active Substitute a current-controlled current source and a battery, which is the forward active model of the transistor to model the circuit. Note that you will have to change one of the attributes on the current-controlled current source (part F). The gain, which has a default value of 1, should be changed to whatever the beta is for the problem.

Saturation Replace the transistor with two batteries.

Checks on the PSpice calculations Both PSpice models will yield answers when you run the simulation. You must check to see if the currents and voltages calculated in PSpice match the boundary conditions of the model IE ≥ 0, IC ≥ 0, and IB ≥ 0 Forward active: VCE > 0.1V and IC = b IB If not, then you have chosen the wrong model. Saturaion: IC < b IB

In this example The forward active model was correct VCE = 0.7V IC = 4.2mA = b IB, where IB = 86mA Currents calculated using the saturation model were IC = 4.9mA > b IB, where IB = 84mA