关键词: 运算跨导放大器, 乘法数模转换器, 增益自举电路, 零极点, 密勒补偿, 模数转换器

Abstract: Operational transconductance amplifier is an important part of multiplying digital to analog converter (MDAC) module in pipelined ADC. A kind of operational transconductance amplifier (OTA) for a 1 GSample/s 14 bit pipelined ADC is designed and implemented. Due to the application needs in the field of wireless communication, the operational transconductance, which can meet the requirements of ADC’s speed and accuracy needs to have differential output of 1.6 V implemented at the 1.8 V power supply. The telescopic structure with the gain bootstrapping circuit enables the OTA to have both high gain bandwidth product (GBW) and high DC gain, and the common source amplifier is designed as the second stage of the OTA to achieve large output swing. The zeroing resistor and miller compensation enable the OTA to obtain an appropriate phase margin with small power consumption, and the overall power consumption of the OTA can be further optimized with zero-pole analysis. The operational transconductance amplifier is implemented at 40 nm CMOS process. Simulation results show that the DC gain of the operational transconductance amplifier is more than 90 dB, the GBW is more than 17 GHz, and the phase margin is more than 80°, which fully meets the performance requirements of the 1 GSample/s 14 bit pipelined ADC.

Key words: operational transconductance amplifier, multiplying digital to analog converter, gain bootstrapping circuit, zero-pole, miller compensation, analog/digital converter