1
ECE 294 Lab Report
Lab Number and Title: TRANSISTOR COMP. OF 2 BASIC TYPES: MOS & BIPOLAR
Instructor’s name: Adwani, Neel
Date of Experiment
Date of Report Submission
Course & Section Number:
4/28/25
5/4/25
SP25-ECE294006
Names: Jaeyoon L.: (jl2386), Anibal A.: (asa29), Jeraldine R.: (jr899), Ebubechi N. (enn)
1. Objectives
Familiarity with MOSFET, the most used type of transistor today and its comparison with BJT.
Demonstrating extremely high dc impedance of the MOSFET gate. Exploring linear
characteristics and switching behavior of the transistors. MOSFET as voltage controlled device
and BJT as current controlled device. MOS analog switch.
2. Equipment Used
Proto-Board
Analog Universal Meter
Resistance Substitution Box
Portable Analog/Digital Multimeter
Oscilloscope Probe-2
Banana To Alligator-3
BNC To Alligator-1
Scope Probe
Leads
2
3. Introduction
Protoboard - Used for prototyping and assembling circuits without soldering for easier
modification.
Banana to alligator cables - Used for connecting various components in a circuit, especially
when testing or debugging.
Analog Multimeter - Used for measuring electrical parameters such as voltage, current, and
resistance in a circuit. It has a needle that moves across a scale, providing a visual readout of the
measurement.
Resistance Substitution Box – Used to easily switch between different resistor values in a circuit
without physically replacing resistors.
Digital Multimeter - Used for measuring electrical values such as voltage, current, and
resistance. It helps in troubleshooting and testing circuits to ensure they function correctly.
Portable Analog/Digital Multimeter – Measures voltage, current, and resistance in a circuit.
Oscilloscope Probe – 2 – Connects a circuit to an oscilloscope to measure voltage over time.
BNC to Alligator – 1 – Adapts a BNC connector (used on lab instruments) to alligator clips, so
you can attach instruments like oscilloscopes to bare wires or component leads.
Scope Probe – Same as the Oscilloscope Probe. Often includes a switch for 1x/10x attenuation to
handle different voltage levels.
Leads – Flexible wires with connectors (e.g. banana plugs or alligator clips) used to make
temporary or quick connections between circuit components and instruments.
4. Schematics / Circuit Diagrams
4.2
TRANSISTOR AS A SWITCH
4.2.2
MOSFET
4.2.3.
SWITCHING OPERATION OF A MOSFET.
4.3
TRANSISTOR AS AN AMPLIFIER
4.3.1
MOSFET
3
4.3.2
BJT
4
5. Procedure
We began by identifying the polarity of the BJT using an ohmmeter to test the base-emitter and
base-collector junctions. Next, we built switching circuits for both a BJT and an n-channel
enhancement-mode MOSFET, using a lamp to observe switching behavior. We varied the
base/gate resistor (Rx) and measured voltages and currents to determine input and output
resistance. In the MOSFET setup, we noted the effect of static charge and gate float conditions.
We then replaced the lamp with two 100Ω resistors and applied a square wave through a 10kΩ
resistor to study the switching behavior at increasing frequencies, observing waveforms with a
5
scope. Finally, we constructed amplifier circuits for both MOSFET and BJT to measure
drain/collector current as a function of gate/base voltage or current, respectively, and determined
threshold voltage and current gain (β). We also tested both transistors using a curve tracer and
built a basic MOSFET analog switch to demonstrate voltage-controlled switching of analog
signals.
6. Data & Observations
4.1
POLARITY OF THE BIPOLAR TRANSISTOR
4.2
TRANSISTOR AS A SWITCH
● 4.2.1
BJT
● 4.2.2
MOSFET
6
● 4.2.3.
SWITCHING OPERATION OF A MOSFET.
7
4.3
TRANSISTOR AS AN AMPLIFIER
● 4.3.1
Vg
8
MOSFET
Id
1
0.000004664
2
0.000009061
3
0.00006994
4
0.00000744
● 4.3.2
BJT
Vbb
Vb
Ib(Vbb)
Ib(Vb)
0.15106
0.996
32.1mA
21.2 *10^-6
4.4
Vb
TRANSISTOR CHARACTERISTICS
Vc
0.247
0.222
0.239
0.223
0.266
0.238
4.5
MOSFET AS AN ANALOG SWITCH
9
7. Results and Analysis
The BJT showed clear current-controlled behavior, requiring base current to activate switching
and amplification. In contrast, the MOSFET operated effectively with minimal gate current,
confirming its high input impedance and voltage-controlled nature. Switching tests revealed
faster response in the MOSFET at higher frequencies. Amplifier configurations demonstrated
that MOSFET drain current increased exponentially with gate voltage above threshold, while
BJT collector current scaled with base current, confirming transistor operation principles.
8. Conclusions
This lab demonstrated the key differences between MOSFETs and BJTs. We confirmed that
MOSFETs are voltage-controlled with high input resistance, while BJTs are current-controlled
and require base current to operate. Both transistors functioned as switches and amplifiers, but
MOSFETs showed better suitability for low-power and analog switching applications. The
experiments highlighted the unique advantages of each type in different circuit roles.
9. References
Randy H. Katz, Contemporary Logic Design, The Benjamin/Cummings Publishing Co., 1994
10
0
