A Low Noise High CMRR Current-Mode Amplifier

• Main Authors: Bing-shiun Tang, 湯秉勳
• Other Authors: H. C. Chow
• Format: Others
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/81511236881776905994

碩士 === 長庚大學 === 電子工程學研究所 === 96 === Biomedical signals, such as EEG/ECG signals, are characterized by their low voltage-levels and very low frequencies. Thus, a current-mode instrumentation amplifier (IA) must exhibit very low input-referred noise. Biomedical signals are acquired and transferred to the voltage signals with amplitude of several milli-volts. The IA must have high input impedance, low output impedance, limited bandwidth, adjustable gain and low power consumption. Additionally, it must have adequate gain, high power-supply rejection ratio (PSRR) and high common-mode rejection ratio (CMRR) to suppress noise. To reduce the noise of the amplifier, two design methods have been implemented to improve the prior art in this thesis. 1. PMOS input is used because its flicker noise is less than that of NMOS. 2. Lateral PNP BJT input is used because it has better noise characteristics than that of MOS transistors. In this thesis, a 1.8-V current-mode amplifier has been proposed for both low power and adjustable gain for various biomedical signal processing with an external resistor. Based on post-layout simulation results, the proposed current-mode amplifier achieves an overall gain of 84.2 dB (PMOS type) 、92.5dB (BJTtype), input-referred noise of 107.7443n V/√Hz (PMOS type) 、54.9401n V/√Hz (BJT type), CMRR of 25.3 dB (PMOS type)、121.8dB (BJT type), power consumption of 61.5043 uW (PMOS type)、65.6571uW (BJT type) at a 1.8-V supply using a standard 0.18-um CMOS technology.