▁op - amps ▁and ▁precision ▁resist ors , ▁but ▁are ▁also ▁available ▁in ▁integrated ▁circuit ▁form ▁from ▁several ▁manufact ur ers ▁( including ▁Texas ▁Inst ru ments , ▁Anal og ▁Dev ices , ▁Linear ▁Technology ▁and ▁Maxim ▁Integr ated ▁Product s ). ▁ ▁An ▁IC ▁instrument ation ▁ampl ifier ▁typically ▁contains ▁closely ▁matched ▁las er - trim med ▁resist ors , ▁and ▁therefore ▁offers ▁excellent ▁common - mode ▁re jection . ▁Ex amples ▁include ▁IN A 1 2 8 , ▁AD 8 2 2 1 , ▁L T 1 1 6 7 ▁and ▁MAX 4 1 9 4 . ▁ ▁Inst rument ation ▁Am pl ifiers ▁can ▁also ▁be ▁designed ▁using ▁" Ind irect ▁Current - feed back ▁Architecture ", ▁which ▁extend ▁the ▁operating ▁range ▁of ▁these ▁ampl ifiers ▁to ▁the ▁negative ▁power ▁supply ▁rail , ▁and ▁in ▁some ▁cases ▁the ▁positive ▁power ▁supply ▁rail . ▁This ▁can ▁be ▁particularly ▁useful ▁in ▁single - supp ly ▁systems , ▁where ▁the ▁negative ▁power ▁rail ▁is ▁simply ▁the ▁circuit ▁ground ▁( G ND ). ▁Ex amples ▁of ▁parts ▁util izing ▁this ▁architecture ▁are ▁MAX 4 2 0 8 / MAX 4 2 0 9 ▁and ▁AD 8 1 2 9 / AD 8 1 3 0 . ▁ ▁Types ▁ ▁Fe ed back - free ▁instrument ation ▁ampl ifier ▁Fe ed back - free ▁instrument ation ▁ampl ifier ▁is ▁the ▁high ▁input ▁imped ance ▁differential ▁ampl ifier ▁designed ▁without ▁the ▁external ▁feedback ▁network . ▁This ▁allows ▁reduction ▁in ▁the ▁number ▁of ▁ampl ifiers ▁( one