Equipment:
You must make up a complete equipment list and have your instructor review it before you start.
 

Components:

• Q1 - 2N3904 NPN Transistor
• R1 - 100 KW

Objectives:

• To use an ohm meter to determine the forward and reverse resistance of transistor pn junctions
• To use the diode test function of the Keithley Model 175 to measure transistor pn junction characteristics
• To obtain several transistor characteristic curves by plotting the information taken from a transistor test circuit
• To obtain the IV Characteristic Curves for a transistor by using a Tektronix Model 571 Curve Tracer
• To determine the h parameters (h_ie, h_re, h_fe and h_oe) of a Transistor
• To verify manufacturer specifications

1.-  (HW) Transistor specifications, ratings and symbols

Refer to the specifications for the 2N3904 and find the following information:

1. transistor type
2. maximum power it can dissipate at 25⁰ Celcius
3. maximum collector current rating
4. maximum collector to emitter voltage rating
5. operating temperature range
6. minimum and maximum h_fe
7. the emitter to base breakdown voltage
8. h_ie @ I_C = 5 mA
9. h_fe @ I_C = 5 mA
10. h_oe @ I_C = 5 mA
11. h_re @ I_C = 5 mA
12. V_BE @ V_CE = 1.0 V and I_C = 5 mA

 

• Place all this information in Data Table A - 2N3904 Specifications & Ratings.

• Identify the base, collector and emitter pins of the 2N3904. Draw a pin out diagram of this device and call it Figure A - Pin Out Diagram of 2N3904.

• Draw and label the electrical symbols for a NPN and PNP transistor. Place this information in Figure B - Types of Transistors & Their Electrical Symbols.

2.-  Static Measurements

1. (HW) From experiment #1, what would you think the forward-biased Resistance values are for base-emitter junction and the base-collector junction of Q₁ ?  Explain how do you get that values from.

 
2. Set the ohm meter to the 200 kW scale. Measure and record the forward bias resistance of the base-emitter junction and the base-collector junction in Q₁. Set the ohm meter to its highest scale and measure and record the reverse bias resistance of both junctions in Q₁. Place this information in Data Table B - 2N3904 Characteristics.

 
3. (HW) Explain what the Keithley Model 175 diode test would indicate if either the base-emitter or base-collector pn junctions were working properly.

 
4. Test both pn junctions of Q₁ with the diode test function of the Keithley Model 175. Measure and record the forward and reverse biased readings of Q₁ of both of these junctions. Include this information in Data Table B.

 

3.- (HW) I_B vs V_BE for different values of V_CE with ORCAD

Plot I_B vs V_BE for different values of V_CE. This plot is a SPICE parametric DC sweep. The ranges for I_B and V_BE are 50 mA and 1Volt. V_CE should vary from 0 to 10 Volts with 1 Volt increments. Label this plot "Plot A - ORCAD I_B vs V_BE".
 
 
 
 

4.-  I_B vs V_BE Measurements Using a Test Circuit

Assemble the circuit shown in Figure # 1.
a)  Set V_CE = 1 V_DC and vary I_B from 5 to 50 mA in steps of 5 mA and record the values of I_B and V_BE  for each step.

b)  Set V_CE = 10 V_DC and once again vary I_B from 5 to 50 mA in steps of 5 mA and record the value of  I_B and V_BE for each step.

Place all this information in Data Table # 1 - Base Characteristics. Plot I_B vs. V_BE in Graph # 1 - 2N3904 Base Characteristics (be sure to annotate the V_CE lines for V_CE = 1V and V_CE = 10V).
 
 
 

5.- (HW) I_C vs V_CE for different values of I_B with ORCAD

1. Plot I_C vs V_CE for different values of I_B. This plot is a SPICE parametric DC sweep. The ranges for I_C and V_CE are 10 mA and 10 Volts. I_B should vary from 0 to 50 mA with 5 mA increments. Label this plot "Plot B- ORCAD I_C vs V_CE".

 
2. Repeat part a) but for the value of b equal to 10. Why there is a difference in the graph when you change b value? 

Hint: To change b value, you have to get into the NS3904 SPICE library file,change the value and save the file.

6.-  I_C vs V_CE Measurements Using a Test Circuit

Using circuit of Figure #1:
a)  Set I_B = 20 mA and vary V_CE from 0 to 2 V_DC in 0.2 V_DC steps. Then vary V_CE from 2 V_DC to 10 V_DC in 2.0 V_DC steps.   Record the value of  I_C and V_CE for each step.

b)  Set I_B = 40 mA and vary V_CE from 0 to 2 V_DC in 0.2 V_DC steps. Then vary V_CE from 2 V_DC to 10 V_DC in 2.0 V_DC steps.
record the value of  I_C and V_CE for each step.

Place all this information in Data Table # 2 - IV Characteristic Data. Plot I_C vs. V_CE in Graph # 2 - 2N3904 Characteristic Curves (be sure to annotate the I_B lines for I_B = 20 mA and IB = 40 mA).
 
 
 

7.-   I_C vs V_CE Measurements Using a Curve Tracer

Obtain a copy of a family of 10 curves for the 2N3904 from the Tektronix Model 571 Curve tracer. Set I_C to be no greater than 10 mA, V_CE to be no greater than 10 V and I_B to step 10 times in 5 mA steps (be sure to annotate the I_B lines).  Label this plot as "Plot C - I_C vs V_CE Measurements Using a Curve Tracer"
 
 
 

8.- Data Analysis

1. Determine h_ie, h_re, h_fe, and h_oe when V_CE = 5V and I_C = 5 mA from Graph #1 and Graph #2.

Hint:  Use the handout that will be given in class to find those values.
2. Compare your results to the manufacture’s specifications.
3. Determine the values of g_m, r_p, r_e, and r_o in terms of the h parameters.
4. Determine the values of g_m, r_p, and r_e from the following formulas:

6. Compare the values obtaine in c) and d)