High accuracy dynamic adjusting voltage source for cell impedance tomography application

Abstract

This paper presented a high accuracy voltage source with current limiting function. A high-speed (250 MHz), high-resolution (16 bit) dual DAC is used for generating stimulate voltage by DDS technique. The amplitude of source could be adjusted by wide bandwidth, low noise variable gain amplifiers from -11 to +51 dB. The 4-Opamp architecture is applied to realize a high gain, high-accuracy variable gain instrument amplifier circuit for tiny current sensing. By using analog comparator to convert over-current time into length of digital pulse, the FPGA could monitor the amplitude of current in real-time. Evaluation results show that system has good SFDR performance and fast response speed. With the advantages of accuracy and bandwidth, it is suitable for cell impedance tomography application. © 2011 Springer-Verlag.