ECEN 3711 Logic Inverters with Bjts Using Pspice Lab #9

ECEN 3711Logic Inverters with BJTs using PSpice [10 points]Lab #9

Purpose: To use OrCAD/PSpice to study the basic TTL inverter constructed from two BJTs.

Procedure: Your PSpice work should always include labeled schematics, PROBE plots, and .OUT files, all with your notes on each as appropriate to explain your work in this report. You may carefullyedit the .OUT file to eliminate extra spaces andpage headers to minimize printing. Be sure to orient your pages correctly with the bottom of landscape pages to the right. [1 pt]

1. Build the circuit shown with OrCAD/PSpice. Use values of F and R obtained from the previous lab for parameters BF and BR, resp., in the Q1 and Q0 Q2N2222 PSpice model. You should use a single model for both BJTs. [0.5 pt]
2. Obtain one or more plots of Vout vs Vin for this circuit. Be sure to generate smooth plots. Tell how you accomplished this. [1.5 pts]
3. Obtain one or more plots of the Iin versus Vin characteristics for this circuit. Unlike the experimental lab measurements, it is much easier with PSpice to just vary the Vin DC source and plot its current being careful to plot the correct polarity. Discuss the magnitudes and polarity of Iin as Vin varies over the 0 to 5 V range. [2 pts]
4. If you have experimental results from the previous lab, compare them with these PSpice results by placing experimental points on the PSpice curves. Otherwise discuss from memory. [1 pt]
5. Study this circuit in detail finding the voltages which cause Q1 to switch between forward and inverse modes. Use extra plots, tabulation of values, bias displays, or whatever else helps you present a detailed description of the circuit’s behavior. [1.5 pts]
6. Now build the TTL circuit in the text (Fig 17.24, p1283) with a single input, and repeat the Vout vs Vin study. Use 2N2222 model parameters which make it more like a typical IC BJT. For example, use BF=25, BR=0.1, and also reduce the values of IS and ISE to 1/10th of their PSpice default values. Compare this circuit’s results with the circuit above. [1.5 pts]
7. Discuss this PSpice study and its circuits.[1 pt]

Note that the use of V-probes on a circuit to pick up voltages for plots may seem easy, but is not always a good approach. For example, if you are plotting output versus input with input varying, and you put a V-probe on the input voltage, this will give you a plot of input versus input. This is a useless plot since it is a straight line with a slope of 1. Do not do this! Ask your instructor if you do not understand what this means.

P.Munro 01-Oct-15 4:02 PM