Dual 7.5W Audio Power Amplifier Circuit# AN7158N Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The AN7158N is a dual-channel audio power amplifier IC primarily designed for stereo audio applications requiring moderate output power. Typical implementations include:
Audio Amplification Systems
- Stereo Hi-Fi Systems : Provides 7.5W per channel (typical) into 4Ω loads with ±15V supply
- Car Audio Systems : Operates effectively in automotive environments with proper voltage regulation
- Home Theater Systems : Suitable for surround sound channel amplification
- Portable Audio Devices : When paired with efficient speakers and adequate power supply
Public Address Systems
- Small to medium venue sound reinforcement
- Background music systems for commercial establishments
- Intercom and paging systems
### Industry Applications
- Consumer Electronics : Home audio systems, portable speakers, television audio sections
- Automotive : Car stereo head units, auxiliary audio amplifiers
- Professional Audio : Small mixing console output stages, monitor speaker systems
- Industrial : Alarm systems, industrial audio signaling devices
### Practical Advantages
Strengths:
- High Power Output : Capable of delivering 7.5W per channel with low distortion
- Built-in Protection Circuits : Thermal shutdown and overcurrent protection
- Wide Operating Voltage : ±7V to ±15V supply range
- Minimal External Components : Requires few external components for basic operation
- Good Thermal Performance : Multiwatt15 package facilitates heat dissipation
Limitations:
- Moderate Power Output : Not suitable for high-power applications (>15W)
- Heat Management Required : May require heatsinking at higher power levels
- Limited Frequency Response : Optimized for audio band (20Hz-20kHz)
- Component Matching : Requires careful selection of external components for optimal performance
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Power Supply Issues
- Pitfall : Inadequate power supply decoupling causing oscillation and noise
- Solution : Implement 100μF electrolytic and 100nF ceramic capacitors close to power pins
- Pitfall : Voltage spikes exceeding maximum ratings
- Solution : Use transient voltage suppressors and proper regulation
Thermal Management
- Pitfall : Insufficient heatsinking leading to thermal shutdown
- Solution : Calculate thermal requirements based on expected power dissipation
- Pitfall : Poor PCB thermal design
- Solution : Use thermal vias and adequate copper area for heat spreading
Oscillation Problems
- Pitfall : High-frequency oscillation due to improper layout
- Solution : Keep input and output traces separated, use ground planes
### Compatibility Issues
Input Signal Compatibility
- Compatible with standard line-level inputs (0.5-2V RMS)
- May require input attenuation for higher-level signals
- DC-coupled inputs possible with proper biasing
Load Compatibility
- Optimal performance with 4-8Ω speakers
- Can drive 16Ω loads with reduced power output
- Not recommended for loads below 4Ω without derating
Power Supply Requirements
- Requires dual symmetric power supply (±7V to ±15V)
- Compatible with standard audio power supply designs
- Needs adequate current capability (1.5A peak per channel)
### PCB Layout Recommendations
Power Supply Layout
- Use star grounding technique for power and audio grounds
- Place decoupling capacitors within 10mm of power pins
- Implement separate ground returns for high-current and signal paths
Signal Routing
- Keep input traces short and away from output traces
- Use ground plane beneath sensitive input stages
- Route output traces with adequate width for current carrying capacity
Thermal Management
- Provide sufficient copper area for heatsinking
- Use thermal vias to distribute heat to inner layers
