Electronics 102 - Lesson 3 - Answers

Question 1

There should be no effect. To demonstrate it, change the DC offset value in the definition for Source V1 and redo the simulation.

Setting R3 to 190 k gets you very close with the 2N2222 transistor.

Here is the plot with a 2N3055 transistor and the original 100k resistor for R3:

Here is Eq 3:

We can neglect Vb (0.7 V) compared to Vc (true as long as Vc > a few volts):

We can neglect the base current compared to the collector current (true as long as the gain is high, i.e. > 50):

If we know the voltage across R1 and R1's value, we can compute the current through it:

Replace I_c in Eq 4 with the value of I(R1) from Eq 6:

We wanted Vc to be half of Vs, so replace Vs/2 with Vc in Eq 7

We can simplify this to:

Last Updated: May 11 2008 16:44:11