LM4651-LM4652: 170 Watt Class D Audio Power Amplifier

The combination of class D amplifier controller LM4651and power MOSFET package LM4652 gives compact and robust high efficiency class D power amplifier solution. This circuit is ideal for car booster amplifier, active speaker/subwofer, home theater, or PC’s multimedia sound system.  The maximum efficiency 85% is obtained at 125W power output condition. The total harmonics distortion is 10% at full power output of 170W. For better fidelity, the THD at 10W is only 0.3% for 10-500Hz input signal driving  4 ohm speaker. The control of this class D amplifier is done by LM4651, and here are the main features of this controller:

• Conventional pulse width modulation.
• Turn-on soft start and under voltage lockout.
• 50kHZ to 200kHz switching frequency range.
• Externally controllable switching frequency.
• Integrated error amp and feedback amp.
• 15 Lead TO220 isolated package.
• Self checking protection diagnostic.
• Over modulation protection (soft clipping).
• Short circuit current limiting and thermal shutdown protection.

The power supply voltage cannot exceed (+-) 22V, and also, the output stage will be turned off when the supply voltage drops under 10.5V to prevent under-voltage failure both for the circuit and for the battery (if implemented for car audio application). [Circuit’s schematic diagram source: National Semiconductor Application Notes]