An apparatus and method for on-chip bias measurement of an analog signals
on an integrated circuit with a switchable analog-to-digital converter
capable of performing testing and other types of processing. Analog
signal test locations are selected for testing by a test input selector
which is in turn controlled by a controller on an integrated circuit,
such as an imager chip. Test locations are connected to one or more
analog-to-digital converters through the test input selector. The
analog-to-digital converter(s) output a test measurement digital output
to either test equipment or an on-chip calibration circuit. Test
equipment or on-chip calibration circuits adjusts imager component bias
or other operating parameters used in chip or device operation based on
output from the analog-to-digital converter(s).