amps . ▁These ▁are ▁arranged ▁so ▁that ▁there ▁is ▁one ▁op - amp ▁to ▁buffer ▁each ▁input ▁(+ , − ), ▁and ▁one ▁to ▁produce ▁the ▁desired ▁output ▁with ▁ade qu ate ▁imped ance ▁matching ▁for ▁the ▁function . ▁ ▁The ▁most ▁commonly ▁used ▁instrument ation ▁ampl ifier ▁circuit ▁is ▁shown ▁in ▁the ▁figure . ▁ ▁The ▁gain ▁of ▁the ▁circuit ▁is ▁ ▁The ▁right most ▁ampl ifier , ▁along ▁with ▁the ▁resist ors ▁label led ▁ ▁and ▁ ▁is ▁just ▁the ▁standard ▁differential ▁ampl ifier ▁circuit , ▁with ▁gain ▁= ▁ ▁and ▁differential ▁input ▁resistance ▁= ▁ 2 · . ▁The ▁two ▁ampl ifiers ▁on ▁the ▁left ▁are ▁the ▁buff ers . ▁With ▁ ▁removed ▁( open ▁circ u ited ), ▁they ▁are ▁simple ▁unity ▁gain ▁buff ers ; ▁the ▁circuit ▁will ▁work ▁in ▁that ▁state , ▁with ▁gain ▁simply ▁equal ▁to ▁ ▁and ▁high ▁input ▁imped ance ▁because ▁of ▁the ▁buff ers . ▁The ▁buffer ▁gain ▁could ▁be ▁increased ▁by ▁putting ▁resist ors ▁between ▁the ▁buffer ▁in ver ting ▁inputs ▁and ▁ground ▁to ▁sh unt ▁away ▁some ▁of ▁the ▁negative ▁feedback ; ▁however , ▁the ▁single ▁res istor ▁ ▁between ▁the ▁two ▁in ver ting ▁inputs ▁is ▁a ▁much ▁more ▁elegant ▁method : ▁it ▁increases ▁the ▁differential - mode ▁gain ▁of ▁the ▁buffer ▁pair ▁while ▁leaving ▁the ▁common - mode ▁gain ▁equal ▁to ▁ 1 . ▁This ▁increases ▁the ▁common - mode ▁re jection ▁ratio ▁( C MR R ) ▁of ▁the ▁circuit ▁and ▁also ▁enables ▁the ▁buff ers ▁to ▁handle