COMPLEMENTARY SILICON POWER TRANSISTORS# 2N3773 NPN Power Transistor Technical Documentation
Manufacturer : MOT (Motorola Semiconductor)
## 1. Application Scenarios
### Typical Use Cases
The 2N3773 is a robust NPN silicon power transistor designed for high-power amplification and switching applications. Its primary use cases include:
- Power Amplification : Audio power amplifiers (50-150W range), RF power amplifiers in communication equipment
- Switching Applications : High-current switching regulators, motor controllers, relay drivers
- Linear Regulation : Series pass elements in power supplies up to 140V
- Industrial Control : Solenoid drivers, actuator controllers, heavy-duty industrial automation
### Industry Applications
- Audio Equipment : High-fidelity audio amplifiers, public address systems
- Power Supplies : Linear power supplies, battery chargers, UPS systems
- Industrial Machinery : Motor drives, welding equipment, heavy motor controllers
- Automotive Systems : Ignition systems, high-power automotive electronics
- Telecommunications : RF power amplification in transmitter stages
### Practical Advantages and Limitations
Advantages:
- High current capability (16A continuous collector current)
- Excellent power handling (150W power dissipation)
- High voltage rating (140V VCEO)
- Robust construction with metal TO-3 package for superior thermal performance
- Wide operating temperature range (-65°C to +200°C)
- Good DC current gain (15-60 at 4A, 4V)
Limitations:
- Relatively slow switching speed (typical fT of 0.2 MHz)
- Requires substantial heat sinking due to high power dissipation
- Larger physical size compared to modern plastic packages
- Higher cost than equivalent modern devices
- Limited availability as newer technologies have superseded this design
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Thermal Management Issues:
- Pitfall : Inadequate heat sinking leading to thermal runaway
- Solution : Use proper thermal compound and calculate heat sink requirements based on maximum power dissipation and ambient temperature
Secondary Breakdown:
- Pitfall : Operating outside safe operating area (SOA) causing device failure
- Solution : Always design within specified SOA curves and use derating factors
Base Drive Requirements:
- Pitfall : Insufficient base current causing saturation voltage issues
- Solution : Ensure base drive circuit can provide adequate current (typically 1-2A for full saturation)
### Compatibility Issues with Other Components
Driver Circuit Compatibility:
- Requires high-current driver stages (compatible with TTL/CMOS with appropriate buffer stages)
- May need level shifting when interfacing with low-voltage control circuits
Protection Circuit Requirements:
- Essential to include overcurrent protection (fuses, current sensing)
- Voltage spike protection (snubber circuits, TVS diodes) due to inductive loads
- Reverse bias SOA protection for inductive switching applications
Thermal Interface Materials:
- Compatible with standard thermal compounds and insulating pads
- TO-3 package requires proper mounting hardware and torque specifications
### PCB Layout Recommendations
Power Routing:
- Use wide copper traces for collector and emitter connections (minimum 3mm width per amp)
- Implement star grounding for emitter connections to minimize ground loops
- Place decoupling capacitors close to device terminals
Thermal Management Layout:
- Provide adequate copper area for heat dissipation
- Use thermal vias when mounting on PCB with heat spreader
- Ensure proper clearance for heat sink mounting
Signal Isolation:
- Keep high-current paths separate from sensitive signal traces
- Implement proper spacing between base drive circuitry and power sections
- Use ground planes for noise reduction
Mounting Considerations:
- Follow manufacturer-recommended mounting torque (typically 6-8 in-lbs)
- Use insulating washers and thermal compound
