1-V operational amplifier with rail-to-rail input and output ranges

A bipolar operational amplifier (OA) with rail-to-rail input and output ranges which can operate at supply voltages down to 1 V is presented. At this supply voltage, the input offset voltage is typically 1.0 mV in an input common-mode voltage range that extends beyond both supply rails for about 300 mV, with a common-mode rejection ratio (CMRR) between 38 and 100 dB, depending on conditions. The output voltage can reach both supply rails within 100 mV, the output current is limited to ±10 mA, the voltage gain is 100 dB, and the bandwidth is 450 kHz. The die is 2.5×5.5 mm². Qualities such as offset, input-bias current, and CMRR are improved when the supply voltage is increased and the dynamic level shift is autonomically turned off. The OA has been protected against unintentional reversal of the output signal when the inputs are substantially overdriven. The output stage of the circuit consists of two full complementary composite transistors, whose HF characteristics have been improved by internal Miller compensation and linearization of the transconductance