A Low Voltage,Rail-to-Rail,Class AB CMOS Amplifie

　　Class AB output stages are increasingly popular in today’s low voltage battery-powered

　　electronics where amplifier applications demand high efficiency as well as rail-to-rail operation.

　　In the era of portable equipment， low supply voltage and low power consumption are intrinsic

　　traits ［1］。 Performance requirements are also becoming more stringent， leaving the designer with

　　more difficult specifications to fulfill and less flexibility with which to do it. For instance， low

　　output impedance is generally desired， but classical source-follower configurations are not

　　allowed in low voltage applications. Dynamic range is already limited by low battery voltages

　　and source followers take too much of that range away to be viable solutions. In fact， most low

　　voltage class AB output stages have inherently high output impedance because they necessarily

　　employ common-source configurations ［2-4］。 On the other hand， amplifiers with source follower

　　output stages typically suffer from output voltage swing limitations， which are severe in low

　　voltage applications. Ideally， though， one would like to combine the characteristics of sourcefollowers and common-source gain stages in the same circuit to achieve low output impedance，

　　rail-to-rail operation， and high current-drive capability. The one previously reported topology

　　that implements this combination is not a low voltage solution and， moreover， has load-rang