关键词: 低电压, 轨到轨, 恒定跨导

Abstract: A low voltage and rail to rail operational amplifier with constant transconductance, as an error amplifier used for BUCK type DC-DC to adjust the output voltage is designed. This operational amplifier is compiled with two stages. The input stage is adopted by complementary differential pairs to realize the input voltage rail to rail, and a double current mirror is used to realize the constant transconductance. In the output stage, the class AB amplifier is adopted to improve output voltage swing and efficient, and rail to rail output voltage is realized. Using CSMC 0.25 μm EN BCDMOS process to design this circuit, the experimental results show that, the gain is 124 dB, unit gain bandwidth is 5.76 MHz, the phase margin is 59.9 ℃, the input transconductance is 5.2 mΩ^_1 , the CMRR is 123 dB, the input common signal range is 0-2.8 V, and the output voltage swing is 0-2.8 V, when the supply voltage is 2.8 V and output load capacitance is 160 pF, the load resistance is 10 kΩ.

Key words: low voltage, rail to rail, constant transconductance