9.3.2.1 Advantages of Fully Differential Amplifiers
Mid-supply bypass capacitor, CBYPASS, not required:
The fully differential amplifier does not require a mid-supply bypass capacitor. Any shift in the mid-supply affects both positive and negative channels equally and cancels at the differential output.
Improved RF-immunity:
GSM handsets save power by turning on and shutting off the RF transmitter at a rate of 217 Hz. This 217 Hz burst often couples to audio amplifier input and output traces causing frame-rate noise. Fully differential amplifiers cancel frame-rate noise better than non-differential amplifiers.
Input-coupling capacitors not required, but recommended:
The fully differential amplifier allows the inputs to be biased at voltages other than mid-supply (PVDD/2). The TPA2015D1 inputs can be biased anywhere within the common mode input voltage range, as listed in the Section 7.6 table. If the inputs are biased outside of that range, then input-coupling capacitors are required.
Note that without input coupling capacitors, any dc offset from the audio source will be modulated by the AGC. This could cause artifacts in the audio output signal. Perform listening tests to determine if direct input coupling is acceptable.