PHYS 415 Electronics

Lab 1 Network Theorems

In this lab we will analyze the circuit shown in Figure 1 using the following;

Figure 1
Figure 1
  1. Kirkoff's node law
  2. Kirkoff's loop law
  3. Superposition
  4. Thevenin's Theorem
  5. Norton's Theorem

Kirkoff's node law

The sum of the curents flowing into a node is zero.

With the output current Iout equal to zero, write an equation for the total current flowing into the node labeled Vout. Solve for Vout.

Kirkoff's loop law

The sum of the voltages around a loop is zero.

Again with the load disconnected (Iout = 0.) Add the voltages arround the outer loop (10V plus the voltage across R1 and R2). Assume a current I1 flowing clockwise around the first loop(Through the 10V supply, R1 and the 2mA current source.) Also assume a current I2 flowing clockwise around the second loop (the 2mA current source and R2.) Note that 2mA = I2 - I1.

Solve for I2 and for Vout.

Superposition Theorem

In a linear system the effect of a number of causes is equal to the sum of the effects of each cause acting individually.

Set the current source equal to zero (no current-open circuit). Solve for Vout due to the 10V voltage source. Set the voltage source equal to zero (no voltage-short circuit). Solve for Vout due to the current source. Add these two componets of Vout to find Vout.

Thevenin's Theorem

As seen from a terminal, any linear network appears to be a voltage source in series with a resistor.

Obtain theThevenin equivalent circuit for the crcuit shown in Figure 1 as seen from the Vout terminal.

Thevenin equivalent

Figure 2   Circuit under test and its Thevenin equivalent

Norton's Theorem

As seen from a terminal, any linear network appears to be a current source in parallel with a resistor.

Obtain the Norton equivalent circuit for the crcuit shown in Figure 1 as seen from the Vout terminal.

Norton equivalent

Figure 3   Circuit under test and its Norton equivalent

Simulate the circuit in Figure 1 using PSPICE.

Obtain plots of the output voltage Vout as a function of output current for the circuit and its Thevenin and Norton equivalents.

Breadboard the circuit. Take measurements to verify network theorems.