DIFFERENTIAL AMPLIFIER USING VOLTAGE LEVEL SHIFTING TO ACHIEVE RAIL-TO-RAIL INPUT CAPABILITY AT VERY LOW POWER SUPPLY VOLTAGE

摘要

A differential amplifier coupled between sources ofa high supply voltage (V HH) and a low supply voltage (V LL)contains a pair of differential portions (30 and 32), thatare used to amplify a differential input signal (V I1 andV I2). One of the differential portions is turned on whenthe common-mode voltage of the input signal is in a portionof the supply range extending up to the high supplyvoltage. The other is turned on when the input common-modevoltage is in a portion of the supply range extending downto the low supply voltage. A level-shift circuit (38, 40,42, 44, and 46) selectively raises or lowers the voltagesat input points (P1, P2, P3, and P4) to the differentialportions. The level shifts extend the conductive ranges ofthe differential portions. This enables the amplifier toeahcieve rail-to-rail input capability down to 1 volt orslightlty less for the power supply voltage.