Book Analog Interfacing to Embedded Microprocessors
must be large enough that it looks like a low impedance at all frequencies of
interest. For audio applications, this typically means an electrolytic.
If the amplifier were a single-supply opamp, the AD5220 could be placed
in the feedback network to control the gain. Since the opamp will not drive
the resistor terminals beyond the supply rails, no biasing resistors are needed.
Of course, biasing resistors may be needed to keep the opamp inputs between
the rails.
The Analog Devices AD5203 is a quad digital potentiometer with an
SPI-like serial interface. The AD5203 potentiometers each have 64 positions
and have the same voltage range limitations as the AD5220 (0V to the
positive supply). The AD5203 comes in 24-pin DIP and surface-mount
packages.
The AD5203 has a shutdown feature: by bringing the SHDN pin low, all
four potentiometer wipers are taken to the B terminal. When SHDN goes back
high, the wipers resume their previous position. A typical application for this
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