This project investigates the behavior of real vs ideal electronic switches, with a focus on MOSFET-based switch designs. It includes simulations, physical testing, waveform analysis, and performance evaluation of two different switch configurations.
- Analog Discovery 3 (AD3): Used for generating test signals, capturing waveforms, multimeter and oscilloscope for measurement/verification of ON/OFF behavior.
- LTspice: For simulating both switch designs.
- nMOS and pMOS Transistors: Used in complementary configurations for voltage-controlled switching.
- Ideal vs. Non-Ideal Switch Behavior:
- Compared expected characteristics like zero resistance, infinite OFF resistance, and bidirectional current flow.
- Real-World Testing:
- Verified ON resistance, OFF leakage current, voltage drops, and bidirectionality using real components.
- Two Custom Switch Designs:
- Switch 1: Minimalist design using nMOS, pMOS, and a resistor.
- Switch 2: More complex but efficient complementary configuration using voltage control.
- Measure ON State Resistance:
- Using Ohm’s Law and measured current/voltage drops.
- Measure Leakage in OFF State:
- With the switch open, detect any current that leaks through.
- Test Bidirectionality:
- Reverse terminals and compare performance.
- Verify Voltage Limits:
- Gradually increase supply voltage to detect any operational thresholds.
- Design: Uses complementary nMOS and pMOS with minimal components.
- Simulation & Physical Testing: Performed in LTspice and on breadboard.
- Performance:
- ON resistance: ~345–487Ω
- OFF resistance: Up to 9.2MΩ
- Voltage drop in ON state: ~0.28V
- Successful bidirectional operation
- Trade-offs:
- Simple, low-noise design.
- Limited by AD3’s 0–5V output range.
- Best suited for low-cost, low-complexity applications.
- Design: Enhanced voltage-controlled logic using two MOSFETs.
- Performance:
- ON resistance: ~387–703Ω
- OFF resistance: Over 11MΩ
- Cleaner control logic via VCONTROL pin.
- Slight non-linearities between 1.5–2.5V due to MOSFET saturation.
- Trade-offs:
- Slightly more complex and costly.
- Outperforms BJTs in power efficiency and thermal stability.
- Less suitable for mass production compared to simpler switch designs.
| Switch | ON Resistance (Ω) | OFF Resistance (Ω) | Bidirectional? | Notes |
|---|---|---|---|---|
| Switch 1 | 345 – 487 | ~923k – 9.2M | ✅ Yes | Simple & robust |
| Switch 2 | 387 – 703 | ~1.1M – 12M | ✅ Yes | Controlled via VCONTROL |
- Both switches confirmed bidirectional current flow.
- Minor inconsistencies in switching thresholds due to MOSFET characteristics.
- Measurements matched theoretical expectations closely.
Project 2 Switch 1.asc,Project 2 Switch 2.asc: LTspice schematics for both designs.Project 2 Documentation.pdf: Complete documentation, design process, and analysis.