The common-mode feedback (CMFB) amplifier is implemented with transistors [M.sub.9]-[M.sub.11], which actually resembles a single-ended difference amplifier
. The error measuring the difference between the IA output common-mode voltage, applied to [M.sub.10a] and [M.sub.10b], and the reference common-mode voltage ([V.sub.CM]) applied to [M.sub.10c] and [M.sub.10d], is amplified in order to drive the gates of the bias transistors [M.sub.7].
The first ADC section is a wide-band analog difference amplifier
whose output goes into a 6-MHz analog low-pass filter.
The AD628 is a common-mode difference amplifier
that includes programmable gain and uses an external resistor.
National Semiconductor has expanded its amplifier portfolio with three high common mode difference amplifiers
. The company's linear monolithic precision (LMP[TM]) line addresses precision applications, and the LMP8270, LMP82701 and LMP8272 amplifiers address broad-based applications in industrial, medical and automotive electronics.