Abstract
This paper presents a low-noise chopper operational amplifier using a lateral PNP input stage with bipolar junction transistor (BJT) current mirror base current cancellation. The BJT has a lower noise characteristic than the metal–oxide–semiconductor (MOS) transistor, where low-noise characteristics can be achieved by implanting the BJT to the input stage of the amplifier; however, the base current of the BJT input stage causes low input impedance of the amplifier. The BJT current mirror base current cancellation technique is implemented to enhance the input impedance of the BJT input stage by canceling the base current. BJT current mirror base current cancellation is implemented with a simple scheme using NPN transistors with deep n-well in a generic complementary metal–oxide–semiconductor (CMOS) process. For further noise reduction with the BJT input stage, a chopper amplifier scheme is adopted to reduce low-frequency components such as 1/f noise terms in the low-frequency range. The prototype chip is fabricated in a 0.18-μm CMOS process. The active area of the prototype amplifier is 0.213 mm2. The measured input-referred noise is 5.43 nV/√Hz. The measured input base current of the amplifier with base current cancellation is 67.971 nA. The total amplifier current consumption is 278.3 μA, with a power supply of 3.3 V.
Highlights
In recent years, various products of precision amplifiers for sensor readout applications have been reported [1,2,3,4,5], e.g., low-noise characteristics essential for low speed and precision-sensing readout circuits
The chopper stabilization technique can achieve a low-noise characteristic; ripples caused by modulated low-frequency noises occur, and a large low-pass filter (LPF) is needed to reject those ripples
The chopper amplifier scheme is implemented for further noise reduction with the bipolar junction transistor (BJT) input stage in the low-frequency range by reducing low-frequency components such as 1/f noise terms
Summary
Various products of precision amplifiers for sensor readout applications have been reported [1,2,3,4,5], e.g., low-noise characteristics essential for low speed and precision-sensing readout circuits. Low-noise techniques such as autozeroing and chopper stabilization are widely implemented in low-noise circuit designs [6,7,8,9,10]. The multipath amplifier scheme with chopper stabilization is suitable for precision-sensing, achieving low-noise and low-offset characteristics with a wide bandwidth [11,12,13,14]. Bipolar junction transistors (BJTs) can be implemented in the input stage of the amplifier for achieving lower noise characteristics than metal–oxide–semiconductor (MOS) transistors [15]. A low-noise chopper operational amplifier using a lateral PNP input stage with BJT current mirror base current cancellation is presented. The chopper amplifier scheme is implemented for further noise reduction with the BJT input stage in the low-frequency range by reducing low-frequency components such as 1/f noise terms
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
