The BJT Biasing Circuits.
North South University
Department of Electrical & Computer Engineering
LAB REPORT
Course Name: Analog Electron I (lab)
Course Code: EEE111L
Experiment Number:06
Experiment Name: The BJT Biasing Circuits.
Experiment Date:10/04/2021
Report Submission Date:16/04/2021
Section:11 Group No: 01
Students Name & ID:
1. Mst. Umme Sadia ID: 2011082643
2. Sadia Afrin ID: 2012281643
3. N.m.m Ibrahim Bhuiyan ID: 2013581643
4. Md. Liaquait Hossain Lipu ID: 2012722643
Report Writter: Sadia Afrin 2012281643
Remarks:
Score
Objective:
Study of the BJT Biasing Circuits.
Theory:
Biasing a BJT circuit means to provide appropriate direct potentials and
currents, using external sources, to establish an operating point or Q-point in the
active region. Once the Q-point is established, the time varying excursions of
input signal should cause an output signal of same waveform. If the output
signal is not a faithful reproduction of the input signal, for example, if it is
clipped on one side, the operating point is unsatisfactory and should be
relocated on the collector characteristics. Therefore, the main objective of
biasing a BJT circuit is to choose the proper Q-point for faithful reproduction of
the input signal. There are different types of biasing circuit. However, in the
laboratory, we will study bias and self-bias circuit. In the fixed bias circuit,
shown if figure 7.1, the base current IB is determined by the base resistance RB
and it remains constant. The main drawback of this circuit is the instability of
Q-point with the variation of β of the transistor. In the laboratory, we will test
the stability using two transistors with different β. In the self-bias circuit shown
if figure 6.2, this problem is overcome by using the self-biasing resistor RE to
the emitter terminal.
Figure-7.1 Experimental circuit 1
Equipment and Components:
Serial Component Specifications Quantity
details
1 Transistor 2N3904, BD135 1piece
2 Resistor 470Ω, 560Ω, 10kΩ 1piece each
3 POT 10kΩ, 100kΩ 1piece each
4 DC power supply 1unit
5 DMM as required
Circuit Diagram:
Figure7.1: Experimental circuit 1
Figure 7.1 Experimental circuit 1
Figure 7.2: Experimental circuit 2
Data and Table:
Table 7.1: Data for fixed bias circuit
Transistor IB VC IC
2N3904 92.2uA 2.93V 15.0mA
BD135 93.1uA 5.46V 11.6mA
Table 7.2: Data for self-bias circuit
Transistor IB VC IC
2N3904 44.3uA 2.55V 7.217mA
BD135 58.1uA 2.57V 7.17mA
Graph:
Graph for circuit 7.1
Graph for circuit 7.2
Discussion:
We have learned in this lab how BJT biasing circuits are made. We have
collected two data table for the fixed biased circuit and self-biased circuit. We
found Ic, Ib, Vc values by going through a total of four circuits using two
transistors (2N3904 AND BD135). We have measured all values form four
circuit by multisim software. We successfully built and ran the circuit and also
completed the lab-6 experiment. We have learned that the fixed biased circuit of
this lab is more stable than the self-biased circuit for a greater range of input
signal
Report Questions:
1. Which circuit shows better stability? Explain in the context
of the results obtained in the laboratory.
2. Draw the DC load line for both the circuits and show the Q-
point
graph for circuit 7.1
graph for circuit 7.2
Contribution:
Student name Student ID Contribution
Mst.Umme Sadia 2011082643 Theory, Data, graph
Md. Liaquait 2012722643 Discussion, Objective
Hossain Lipu
N.m.m Ibrahim 2013581643 Report Questions,
Bhuiyan
Equipment
Sadia Afrin 2012281643 Report Questions,
Circuit Diagram
Attachment:
lab-6.pdf
