Preliminary Technical Data
WM7121
APPLICATIONS INFORMATION
RECOMMENDED EXTERNAL COMPONENTS
Figure 1 WM7121 Recommended External Components
A DC-blocking output capacitor is required on the OUTPUT pin, as illustrated in Figure 1. A single
capacitor is required for a single-ended connection. The capacitor must be correctly selected as it
affects the cut-off frequency of the output path. A low cut-off frequency is desirable as it means there
is no significant filtering of the audio bandwidth.
The 3dB cut-off frequency of the output path is given by the equation below, where C is the output
capacitance and R is the input resistance of the other circuit.
A typical recommended configuration, with 1uF DC-blocking capacitor and 20kꢀ minimum input
circuit impedance, gives a 3dB cut-off frequency of 10Hz or less. Tantalum electrolytic capacitors are
particularly suitable for the DC-blocking components as they offer high stability in a small package
size
OPTIMISED SYSTEM RF DESIGN
For optimised RF design please refer to document WAN0278 for further information.
PTD, Rev 2.0, October 2012
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
