Low Power, High Output Current Differential Amplifier# AD8390A Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The AD8390A is a high-performance, dual operational amplifier specifically designed for demanding applications requiring high output current and wide bandwidth. Key use cases include:
Professional Video Equipment
- Broadcast-quality video distribution amplifiers
- HD/SD video line drivers
- Video crosspoint switch buffers
- The device's 310 MHz bandwidth and 0.1 dB flatness to 70 MHz make it ideal for maintaining signal integrity in high-definition video systems
Medical Imaging Systems
- Ultrasound front-end circuits
- Medical monitor drivers
- The high slew rate (1150 V/μs) ensures accurate signal reproduction for diagnostic imaging applications
Test and Measurement Equipment
- Active probe interfaces
- Signal conditioning circuits
- Arbitrary waveform generator outputs
- The ±250 mA output current capability drives demanding loads without performance degradation
### Industry Applications
Broadcast and Professional Video
- Advantages : Excellent differential gain/phase performance (0.01%/0.01°), direct cable driving capability
- Limitations : Higher power consumption compared to general-purpose op-amps may require thermal management in dense layouts
Communications Infrastructure
- Advantages : Stable operation with capacitive loads up to 100 pF, making it suitable for driving long cables
- Limitations : Requires careful attention to power supply decoupling for optimal RF performance
Industrial Control Systems
- Advantages : Wide supply voltage range (±5V to ±12V) accommodates various system requirements
- Limitations : Not recommended for single-supply operation below 10V total supply
### Practical Advantages and Limitations
Key Advantages:
- High output current (±250 mA) enables direct driving of low-impedance loads
- Low distortion (-80 dBc HD2/HD3 at 1 MHz) maintains signal purity
- Thermal shutdown protection prevents device damage under fault conditions
- Disable function reduces power consumption when not active
Notable Limitations:
- Quiescent current of 12 mA per amplifier may be excessive for battery-powered applications
- Requires external compensation for capacitive loads exceeding 100 pF
- Higher cost compared to general-purpose operational amplifiers
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Oscillation Issues
- Pitfall : Unwanted oscillation when driving capacitive loads
- Solution : Add series isolation resistor (2-10Ω) at output when driving cables or large capacitive loads
- Implementation : Place isolation resistor close to amplifier output pin
Thermal Management
- Pitfall : Junction temperature exceeding 150°C during continuous high-current operation
- Solution : Use adequate copper area for heat dissipation, consider thermal vias for multilayer boards
- Implementation : Minimum 1 square inch copper pour per amplifier for SOIC package
Power Supply Rejection
- Pitfall : Poor PSRR at high frequencies affecting performance
- Solution : Implement proper decoupling with multiple capacitor values
- Implementation : 0.1 μF ceramic + 10 μF tantalum within 0.5" of each supply pin
### Compatibility Issues
Digital Control Interfaces
- The disable pin requires TTL/CMOS compatible logic levels
- Incompatible with open-collector outputs without pull-up resistors
- Ensure disable control voltage does not exceed supply rails
Mixed-Signal Systems
- Sensitive to digital noise coupling through substrate and supply lines
- Maintain adequate separation from digital components (minimum 0.5" recommended)
- Use separate ground planes with single-point connection
### PCB Layout Recommendations
Power Supply Routing
- Use star-point configuration for power distribution
- Implement separate analog and digital ground planes
- Route supply traces with minimum 20 mil width for current handling
