A High Signal Swing Class AB Earpiece Amplifier in 65nm CMOS Technology

This paper describes a new circuit solution to implement a high signal swing amplifier for driving a low resistive and high capacitive load. The amplifier is dedicated to operate at a supply voltage of 2.5V driving an earpiece device of a mobile phone by the usage of a standard digital single gate oxide transistor in a 65nm technology. The high linearity is achieved by using a three stage amplifier. To handle the high voltage of 2.5 V with the 1.2 V transistor an innovative transistor cascoding is implemented. A class AB output stage is chosen to ensure a low power consumption. A prototype is realized in a low power 65 nm CMOS technology. The measured THD is lower than 0.04% at the desired audio band of 20kHz