Class-AB Operational Amplifier with Current Domain Slew-Rate Enhancement

Fast settling is a critical target for amplifiers, which is always limited by slew-rate (SR). The conventional solution is to increase the SR by monitoring the input differential-mode voltage of amplifier, which is sensitive to the input offset voltage. In this paper, a current domain slew-rate enhancement (CDSRE) technique for Class-AB operational amplifier (OPA) is proposed. The proposed CDSRE technique detects slew condition and improve slew rate in current domain, and is only valid during slewing, which completely blocked at DC for avoiding multiple operating points. A two-stage OPA with CDSRE was drawn in 0. 35um BCD process and simulated, results show that SR of OPA can be enhanced by factor of 10 to 47. 5V/us, and only cost 1.3% static power consumption, transient response characteristic was significantly improved.