Objective
The objective of this experiment is to explore the characteristics and performance of thin-film resistors in precision circuit applications. This experiment will demonstrate how thin-film resistors contribute to circuit stability and accuracy.
Materials Needed
- Thin-film resistors (various resistance values)
- Precision power supply (0-10V)
- Multimeter (for measuring voltage and current)
- Breadboard and jumper wires
- Operational amplifier (op-amp)
- Test load (e.g., an LED or small motor)
- Optional: potentiometer (for variable resistance)
Theory
Thin-film resistors are manufactured by depositing a thin layer of resistive material on an insulating substrate. They offer superior precision, stability, and low temperature coefficients, making them ideal for high-performance applications. The stability and accuracy of these resistors can be attributed to their low noise and better tolerance compared to standard resistors.
The resistance can be defined as:
R = V / I
Where **R** is the resistance (in ohms), **V** is the voltage across the resistor (in volts), and **I** is the current flowing through it (in amperes).
Steps
-
Set Up the Circuit
Connect the thin-film resistor in series with the operational amplifier on the breadboard. Connect the output of the op-amp to the test load. Ensure all connections are secure and correct.
-
Initial Measurements
Measure the resistance of the thin-film resistor using a multimeter to confirm its rated value. Record this value for further analysis.
-
Apply Power
Turn on the precision power supply and set it to a low voltage (e.g., 1V). Monitor the circuit for any signs of instability or incorrect readings.
-
Measure Voltage and Current
Using the multimeter, measure the voltage across the thin-film resistor and the current flowing through the circuit. Record these values in a data table for analysis.
-
Experiment with Different Resistors
Repeat the measurements using different thin-film resistors to observe how varying resistance values affect circuit performance. This can also include using a potentiometer to adjust resistance dynamically.
Data and Calculations
Record the voltage and current at various resistor values. Below is a sample data table:
| Resistance (Ω) | Voltage (V) | Current (A) | Power (W) |
|---|---|---|---|
| 1k | 5 | 0.005 | 0.025 |
| 2k | 5 | 0.0025 | 0.0125 |
| 4.7k | 5 | 0.00106 | 0.0053 |
Power dissipation for each resistor value can be calculated using the formula:
P = V * I
Conclusion
This experiment demonstrates the effectiveness of thin-film resistors in precision circuits. Their low noise, high stability, and excellent temperature coefficients make them suitable for high-accuracy applications. Understanding the behavior of these resistors helps in selecting appropriate components for designing reliable electronic systems.