A Baseband Ultra-Low Noise SiGe:C BiCMOS 0.25μm Amplifier and its Application for an On-Chip Phase-Noise Measurement Circuit

The design and realization of an ultra-low noise operational amplifier is presented. Its applications are integrated low-frequency noise measurements in electronic devices and on- chip phase-noise measurement circuit. This paper discusses the SiGe:C BiCMOS 0.25 mum design improvements used for low noise applications. The proposed three-stage operational amplifier uses parallel bipolar transistor connection as input differential pair for low noise behavior. This operational amplifier provides both low noise and high gain performances. This operational amplifier has an area of only 660 times 250 mum² with an equivalent input noise floor of only 1.1 nV/ radicHz square root at 10 kHz. The measured noise characteristics (versus total power consumption) are better than those of most operational amplifiers commonly adopted in low-frequency noise measurements. The AC gain is 83 dB and the unity gain bandwidth is 210 MHz, with a total current consumption of 18 mA at 2.5 V supply voltage.