Pre-laboratory exercise

Question

1. (1pt) Obtain the value of Is from a simple simulation of the transistor: using the setup of Fig 4, excluding the resistors,

apply V-0.65V, measure le while Ve> 0.5 V (let Ver 1 V) and use equation 1. Assume that n-1. Use the Q2N2222

BJT in the simulation.

2. (1pt) For the circuit in Fig. 2(a), calculate the current In and Ic, and the voltage Ve for at least 5 input voltages (Vie

0.65, 0.75, 0.85, 0.9 and I V), use Ra-IMG2. B-150.

3.

(1pt) For the circuit in Fig. 2(a), if the Vas was set to 0.1V, what would you expect for the value of Vc.

4. (2pts) Construct the circuit shown in Fig. 4 in OrCAD/Pspice. Place a current marker on the collector of the Q2N2222.

Run a DC Sweep on the Vas voltage source to generate the input characteristics. Do a linear sweep starting at 0 and ending

2V with a linear increment of 5mV. Modify the x-axis variable to be the Vaz voltage, not Vas. Comment on your results

for all regions of the plot.

ECEN325 Laboratory Manual, Lab 5

0.7V

lb

VBB 100

DA

Q1

100

Q2N2222

R2

www

100

Q2N2222

Fig. 4. BJT transistor circuit 2

5. (1pt) Repeat step 4 using a current marker at the base of the Q2N2222, sweeping from 0 to 0.7V. Find the input

impedance by evaluating the slope around V-0.65V; Rin-Re-A/A

6. (2pts) Construct the circuit in Fig.5 in OrCAD/Pspice. Place a current marker on the collector of the Q2N2222.

A secondary DC Sweep is required to generate the output characteristics. First select DC Sweep and set it up

for sweeping VCE from OV to SV with linear increments of 5mV. Then select Secondary Sweep and set that up

for sweeping Is from OuA to 50µA with linear increments of SpA.

100

2

1V

Vcc

Vce

OV

3| Page

Fig. 5. BJT transistor circuit 3

7. (1pt) Find the output impedance R.Av./Ai, from the output characteristics plot.

8. (1pt) Set Ve shown in Fig 5 to 5V and do a linear sweep starting at 0, ending 30μA with a linear increment of

5μA. Find the DC and AC current gain Boc and B. of the transistor. Remember, Boc and B are defined by (3) and

(4) respectively.