Title: Identification of Transistor Terminals and Calculation of Gain in a Common Emitter Transistor Circuit
Abstract
This lab assignment aims to identify the three terminals of a bipolar junction transistor (BJT) using a digital multimeter and to calculate the voltage gain in a common emitter (CE) mode transistor circuit. Understanding the terminal identification and gain calculation is essential for analyzing transistor behavior in electronic circuits.
Introduction
A bipolar junction transistor (BJT) has three terminals: the emitter (E), base (B), and collector (C). Identifying these terminals is crucial for proper circuit configuration. The common emitter configuration is widely used for amplification, and the voltage gain can be calculated based on the input and output voltages. This assignment focuses on identifying the transistor terminals and calculating the gain in a CE mode circuit.
Objective
- To identify the three terminals of a BJT using a digital multimeter.
- To construct a common emitter transistor circuit and calculate the voltage gain.
Hypothesis
It is expected that the terminals of the transistor can be identified accurately using the multimeter, and the voltage gain in the CE mode circuit can be calculated based on the measured voltages.
Materials and Methods
Materials
- Digital multimeter
- NPN transistor (e.g., 2N3904)
- Resistors (for biasing and load)
- DC power supply (or battery)
- Breadboard and connecting wires
- Notebook for recording results
Methods
Part 1: Identification of Transistor Terminals
- Set Up the Multimeter:
- Turn on the digital multimeter and set it to the diode testing mode.
- Identify the Terminals:
- Connect the positive lead of the multimeter to one of the transistor leads and the negative lead to another lead.
- Measure the forward voltage drop. A typical forward voltage drop for a silicon transistor is around 0.6V to 0.7V.
- Repeat this process for all combinations of leads until the three terminals (Emitter, Base, Collector) are identified based on the voltage readings.
Part 2: Common Emitter Circuit Setup
Circuit Construction:
- Construct a common emitter circuit using the identified transistor terminals. Connect the emitter to ground, the collector to a load resistor (R_C), and the base to a biasing resistor (R_B) connected to the power supply.
- Connect a coupling capacitor (if necessary) to isolate the input signal.
Apply Input Signal:
- Apply a small AC input signal to the base of the transistor.
Measure Voltages:
- Measure the input voltage (V_in) at the base and the output voltage (V_out) at the collector using the digital multimeter.
Calculate Gain:
- Calculate the voltage gain (A_V) using the formula: [ A_V = \frac{V_{out}}{V_{in}} ]
Document Findings: Record all measurements and observations in the lab notebook.
Results
Terminal Identification
- Transistor Type: NPN
- Identified Terminals:
- Emitter (E): [Identified Lead]
- Base (B): [Identified Lead]
- Collector (C): [Identified Lead]
Voltage Gain Calculation
| Measurement | Value (V) |
|---|---|
| Input Voltage (V_in) | [Measured Value] |
| Output Voltage (V_out) | [Measured Value] |
| Voltage Gain (A_V) | (\frac{V_{out}}{V_{in}} = \frac{[Measured Value]}{[Measured Value]} = [Calculated Gain]) |
Observations
- The terminals of the transistor were successfully identified using the multimeter.
- The voltage gain calculated from the common emitter circuit was [Calculated Gain].
Discussion
The experiment successfully demonstrated the identification of transistor terminals and the calculation of voltage gain in a common emitter configuration. The use of a digital multimeter allowed for accurate terminal identification, and the gain calculation provided insight into the amplification capabilities of the transistor.
