PAM8009

Document number: DS37224 Rev. 1 - 2

9 of 12

www.diodes.com

January 2015

© Diodes Incorporated

PAM8009

Input Capacitor (Ci)

Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sized capacitor is needed to couple in low

frequency without severe attenuation. But in many cases the speakers used in portable systems, whether internal or external, have little ability to

reproduce signals below 100Hz to 150Hz. Thus, using a large-input-capacitor may not increase actual system performance. In this case, Input

Capacitor (Ci) and Input Resistance (Ri) of the amplifier form a high-pass filter with the corner frequency determined equation below:

Fc = 1/ 2πRi x Ci

In addition to system cost and size, click and pop performance is affected by the size of the input coupling capacitor, Ci. A larger in/out coupling

and is apt to create pops upon device enabling. Thus, by minimizing the capacitor size based on necessary low frequency response, turn on pop

can be minimized.

into the output signal. The noise is from the internal analog reference to the amplifier, which appears as degraded PSRR and THD+N.

reduces clicking and popping noise from power on/off and entering and leaving shutdown.

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