With ICs LM4651 & LM4652
The combination of the LM4651 driver IC and the LM4652 power MOSFET Class D power amplifier IC provides a high efficiency amplifier solution, suitable for self-powered speakers, subwoofers and quality car boosters.
The LM 4651
is a fully integrated conventional pulse width modulator (PWM) driver,
containing undervoltage, short circuit, overmodulation, and thermal
shutdown protection circuitry. The IC features a standby function which
shuts down the pulse width modulation, minimizing supply current.
The LM 4652
is a fully integrated H-bridge Power Mosfet IC in a TO220 power
package. The IC has a built in temperature sensor to alert the LM4651
when the die temperature exceeds the threshold limit.
Used
together, the LM4651 and LM4652 form a simple, compact, efficient, high
quality power audio amplifier solution complete with protection,
normally seen only in Class AB amplifiers.
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The maximum efficiency of this circuit is 85% at 125W with a standby attenuation greater than 100dB. The THD at 10W, 4 ohms, 10 - 500Hz is max. 0.3%. The supply voltage can not exceed ± 22V.
For the best performance a suitable preamplifier is required. With the addition of a preamplifier the gain of the power stage can be greatly reduced to improve performance. The gain should be set to 10 V/V allowing for low gain on the Class D stage with a total system gain high enough to be a complete solution for line level sources.
The input filter used here does not noticeably increase
THD performance but will help to maintain a flat frequency response as
the Q of the output filter changes with load impedance.
Do not attempt to build this amplifier as your first project! Class D high power amplifiers are expensive, difficult to build and a very small error during assembly can lead to total devastation of the power IC or other costly components.
