A 12.6V 130MHz Rail-to-Rail Output Bipolar Amplifier with Overdrive Supply Current Limit

This paper presents a high-voltage high-speed bipolar operational amplifier with rail-rail output (RRO) and negative-rail input (NRI). This amplifier uses a class-AB input stage that can support inputs up to 0.5V below negative rail. To boost the slew rate, a skewed mirror-based technique is used. An input bias current drift cancellation scheme to cancel the temperature drift of input bias current across the input range is proposed. A circuit technique to cancel the distortion due to base-collector capacitance is presented. Amplifiers with class-AB input stage can take high supply current during input overdrive and to limit this, a novel delayed feedback technique is proposed with zero additional power, which can help in multi-channel applications. Designed in a 12.6V bipolar process, this RRO amplifier achieves a gain-bandwidth product of 130MHz, slew rate of 720V/µs, output current drive of 85mA and HD2/HD3 of -106dBc/-95dBc at 1MHz while consuming just 4.5mA of supply current.