A voltage driver using the rail to rail operation in CMOS 0, 25 μm technology

A rail to rail input common mode range is an important requirement in operational amplifiers for some applications. The most common method for implementing full range operation is by using a complementary differential pair. It is simply a compound structure that consists of NMOS and PMOS differential pairs connected in parallel. The compound structure achieves rail to rail operation; however, it produces variations in the transconductance over the input common mode range. The variations obstruct the design of an optimal operational amplifier, to avoid the problem of transconductance variations, an other structure, consists of two op-amps one n-type and the other p-type controlled by a digital control system, is proposed to achieve the ldquorail to railrdquo operation. The layout of this structure is involved with CMOS 0.25 mum technology.