Detailed Instructions for simulating Fig 2.45 in HH in PSpice.
These instructions were written by Brian England in Jan 2003.

1)Open PSpice (MicroSim DesignLab Schematics) - Figure 1

Figure 1

2)Click on Draw -> Place Part (Crtl-P) or the binocular icon

3)Place 2-Q2N3906, 2-r,1-VDC, and 1-GND_EARTH and click close (to find each part just type it in the name and click place, click on the schematics however many times you need that part) - Figure 2

Figure 2

4)Rotate transistors, and resistors to match schematic on page 88.

a.You can use Ctrl - R to rotate and Ctrl - F to flip

5)The load resistor is just a normal resistor and will deal with how to set it up in a minute.

6)Align all parts as in Figure 2.45 and connect wires as shown (You can zoom in to make the circuit easier to work with)- Figure 3

Figure 3

7)Change the value of R1 to 14.4K by clicking on the value, and the value of the VDC to 15 volts

8)Instead of using a variable resistor we will allow PSpice to simulate the variable resistor for us, click on the value of R2 and change it to be ?{RLoad}? (The curly braces are very important) - Figure 4

Figure 4

9)Open the parts lists once again and add the part ?param?

10)Double click on the part, a dialog box will open up

11)Change ?Name 1? to have the value of RLoad, and ?Value 1? to have a value of 1K - Figure 5

Figure 5

12)Click Save Attr, and click OK.There now should be RLoad 1K underneath Parameters

13)We now need to set up the DC Sweep, click on Analysis -> Setup, a menu will show up, check DC sweep and click on the button.

14)Change the values to the following - Figure 6

a.Sweep Variable type - Global Parameter

b.Name - Rload

c.Start Value, End Value, Increment - 1, 100k, 1k

Figure 6

15)A current marker must also be added right before (or after) R2(RLoad)

16)The simulation may now be run by Analysis -> Simulate (or F11) - Figure 7

Figure 7

17)You will notice that the current breaks at about 16K, edit the DC sweep parameters to narrow in on this spot and re run the simulation.You may want to add a voltage marker to see what the voltage is doing at the same time.


1)Is this a good current mirror?Why or Why not?

2)Why does the current mirror break down at this value of the load?