PAM8014 Datasheet, PDF (6/9 Pages) Diodes Incorporated – 3.2W MONO CLASS D AUDIO AMPLIFIER

Application Information
Close Loop Gain (GV)
The close loop gain is set by the ratio of the input resistance RIN and feedback resistance RF(refer to block diagram), and the close loop gain
equation is as follow:
Which RF is set at 124KΩ and RIN is 31KΩ, the GV default is 8V/V, which is 18dB.
Input Capacitors (CIN)
In the typical application, an input capacitor, CIN, is required to allow the amplifier to bias the input signal to the proper DC level for optimum
operation. In this case, CIN and the input impedance RIN form is a high-pass filter with the corner frequency determined in the follow equation:
It is important to consider the value of CIN as it directly affects the low frequency performance of the circuit. For example, when RIN is 31kΩ and
the specification calls for a flat bass response are down to 150Hz. Equation is reconfigured as followed:
When input resistance variation is considered, the CIN is 7nF, so one would likely choose a value of 10nF. A further consideration for this capacitor
is the leakage path from the input source through the input network CIN, RIN and feedback resistor RF to the load. This leakage current creates a
DC offset voltage at the input to the amplifier that reduces useful headroom, especially in high gain applications. For this reason, a low-leakage
tantalum or ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor should face the amplifier
input in most applications as the DC level is held at VDD/2, which is likely higher than the source DC level. Please note that it is important to
confirm the capacitor polarity in the application.
Decoupling Capacitor (CS)
The PAM8014 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output total harmonic
distortion (THD) as low as possible. Power supply decoupling also prevents the oscillations causing by long lead length between the amplifier and
the speaker.
The optimum decoupling is achieved by using two different types of capacitors that target on different types of noise on the power supply leads.
For higher frequency transients, spikes, or digital hash on the line, a good low equivalent-series-resistance (ESR) ceramic capacitor, typically 1μF,
is placed as close as possible to the device VDD pin for the best operation. For filtering lower frequency noise signals, a large ceramic capacitor of
10μF or greater placed near the audio power amplifier is recommended.
How to Reduce EMI
Most applications require a ferrite bead filter for EMI elimination shown at Figure 1. The ferrite filter reduces EMI around 1MHz and higher. When
selecting a ferrite bead, choose one with high impedance at high frequencies, but low impedance at low frequencies.
OUT+
OUT-
Ferrite Bead
Ferrite Bead
200pF
200pF
Figure 1. Ferrite Bead Filter to Reduce EMI
PAM8014
Document number: DS38114 Rev. 1 - 2
6 of 9
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January 2016
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