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Transistor Biasing Lab Guide

This document describes an experiment on transistor biasing. The experiment involves constructing NPN and PNP transistor circuits and measuring currents and voltages at different resistor and supply voltage settings. Key measurements include collector current, emitter current, base-emitter voltage, collector-base voltage, and collector-base current with the emitter open.

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Shannen Joyce Flores
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192 views4 pages

Transistor Biasing Lab Guide

This document describes an experiment on transistor biasing. The experiment involves constructing NPN and PNP transistor circuits and measuring currents and voltages at different resistor and supply voltage settings. Key measurements include collector current, emitter current, base-emitter voltage, collector-base voltage, and collector-base current with the emitter open.

Uploaded by

Shannen Joyce Flores
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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Experiment Number Twelve

TRANSISTOR BIASING

OBJECTIVES :

1. To become familiar with transistor biasing.


2. To demonstrate the procedure in measuring the ICBO (Collector to
Base Current with Emitter Open) of a bipolar junction transistor.

MATERIALS :

1 – Resistor, 100 Ω
1 – Resistor, 820 Ω
1 – Potentiometer, 2.5K Ω

1 – Transistor, NA51
1 – Transistor, NA52
Breadboard
VOM
Dual Regulated DC Power Supply

CIRCUIT DIAGRAMS :
PROCEDURES :

NPN Biasing

1. Construct circuit number one as shown.


2. Set R2 at maximum resistance. This will result in a minimum bias current.
Measure IE, IC, VBE and VCB. Record their values in Table 1 including the
polarity of the two voltages.
3. Set R2 at minimum resistance. This will result in maximum bias current.
Repeat the measurements in step 2.
4. Power off.

Caution: In this experiment be sure that the voltage across


terminals of power supplies V EE and VCC are at 0
(zero) voltage level whenever “power off” is
mentioned. This is to avoid damage to ammeters
when supply polarities are reversed.

5. Reverse the polarity of VEE. Measure IE, IC, VBE and VCB.
6. Set your ammeter on its most sensitive range (50 μA or lower if available).
7. Power on. Measure and record IC. This is the value of ICBO.
8. Power off.

PNP Biasing

9. Set-up circuit number two.


10. Repeat Steps 2, 3, and 5 for the PNP transistor. Record the results in
Table 1.
11. Repeat Steps 6 and 7 to measure ICBO of the PNP transistor.
12. Grasp the transistor between your fingers. Your body heat causes what
reaction? Note that if your current meter is not sensitive enough, you may
not see any change. If that is the case, place a soldering iron near the
transistor’s body. Gradually increase the heat by slowly decreasing the
distance between the transistor and the soldering iron. Observe the
current. Record your observations.

Caution: Do not overheat the transistor. Excessive heat can


destroy the transistor.
DATA AND RESULTS :

Current (mA) Voltage (V)


Steps Condition
IC IE VEB VCB
2 R2 (Maximum)
0.29 0.29 0.74 5.78
3 R2 (Minimum)
6.79 6.76 0.82 0.51
5 VEE Reversed
0.06 0.01 1.50 6.00
7 ICBO = ___0.06_______ μA
10 R2 (Maximum) 6.32 0.89 0.81 0.82

10 R2 (Minimum)
6.34 3.17 -1.18 0.10
10 VEE Reversed
6.31 -0.26 0.82 0.82
11 ICBO = ___6.31_______μA
Table 1

QUESTIONS :

1. Explain the effect of increasing the value of R 2 to the collector current (I C)


and emitter to base voltage (VEB).

2. Was IC greatest when VEB was minimum? or maximum? Explain why.

3. What is the effect of reversing the polarity of V EE to IC?

4. Where you able to measure ICBO in step 12? If so, what did step 12 prove?
OBSERVATIONS :

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