Radio Transmitter

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Tuesday, March 31, 2009

20 Watt Automotive Power Amplifier

The LM2005 is a dual high power amplifier, designed todeliver optimum performance and reliability for automotive applications. High current capability (3.5A) enables the device to deliver 10W/channel into 2X (LM2005T-S), or 20W bridged monaural (LM2005T-M) into 4X, with low distortion.


  • Wide supply range (8V±18V)
  • Externally programmable gain
  • With or without bootstrap
  • Low distortion
  • Low noise
  • High peak current capability
  • POe20W bridge
  • High voltage protection
  • AC and DC output short circuit protection to ground or across load
  • Thermal protection
  • Inductive load protection
  • Accidental open ground protection
  • Immunity to 40V power supply transients
  • 3§C/W device dissipation
  • Pin for pin compatible with TDA2005

The high current capability of the LM2005 allows it to continuously endure either AC or DC short circuit of the output with a maximum supply voltage of 16V. This will protect the loudspeaker in a bridge mode, when a DC short of the output occurs on one side of the speaker. The device will prevent the speaker from destruction by reducing the DC across the load (bridge mode) to typically less than 2 VDC(VSe14.4V, RLe4X), by an internal current pullback method.

The LM2005 can withstand a constant 28 VDC on the supply with no damage (maximum operating voltage is 18V). The device is also protected from load dump or dangerous transients
up to 40V for 50 ms (every 1000 ms) on the supply with no damage. Protection diodes protect the device driving inductive loads, during which the load can generate voltages greater than
supply or less than ground levels. The protection diodes will clamp these transients to a safe VBE above and below the rails.

The bridge configuration in the picture is designed for applications requiring minimal printed circuit board area and maximum cost effectiveness. The circuit will function with the elimination of bootstrap components R3, C4 and C5 . This will result in less output power by decreasing output voltage swing to the load. By using internal feedback resistors (typically 10 kX), feedback components R2, R3 and C2 may be omitted where closed loop voltage gain accuracy is not critical. The net result is a stable, cost effective circuit that will satisfy many application needs.

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