TPA0103PWPRG4 Datasheet, PDF (30/45 Pages) Texas Instruments – 1.75-W 3-CHANNEL STEREO AUDIO POWER AMPLIFIER

TPA0103
1.75-W 3-CHANNEL STEREO AUDIO POWER AMPLIFIER
SLOS167A – JULY 1997 – REVISED MARCH 2000
APPLICATION INFORMATION
input capacitor, C_I
In the typical application an input capacitor, C_I, is required to allow the amplifier to bias the input signal to the
proper dc level for optimum operation. In this case, C_I and R_I form a high-pass filter with the corner frequency
determined in equation 9.
–3 dB
+ f_c(highpass)
1
2pR_IC_I
(9)
fc
The value of C_I is important to consider as it directly affects the bass (low frequency) performance of the circuit.
Consider the example where R_I is 10 kΩ and the specification calls for a flat bass response down to 40 Hz.
Equation 8 is reconfigured as equation 10.
+ C_I
1
2 p R_I f_c
(10)
In this example, C_I is 0.40 µF so one would likely choose a value in the range of 0.47 µF to 1 µF. A further
consideration for this capacitor is the leakage path from the input source through the input network (R_I, C_I) and
the feedback resistor (R_F) 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 there is held at V_DD/2, which is likely higher
than the source dc level. Please note that it is important to confirm the capacitor polarity in the application.
power supply decoupling, C_S
The TPA0103 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling
to ensure the output total harmonic distortion (THD) is as low as possible. Power supply decoupling also
prevents oscillations for long lead lengths between the amplifier and the speaker. The optimum decoupling is
achieved by using two capacitors of different types that target 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 0.1 µF placed as close as possible to the device V_DD lead works best. For
filtering lower-frequency noise signals, a larger aluminum electrolytic capacitor of 10 µF or greater placed near
the audio power amplifier is recommended.
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