Author:

Keywords:

Science & Technology, Technology, Engineering, Electrical & Electronic, Instruments & Instrumentation, Engineering, 0906 Electrical and Electronic Engineering, 0912 Materials Engineering, 0913 Mechanical Engineering, Nanoscience & Nanotechnology, 4008 Electrical engineering, 4009 Electronics, sensors and digital hardware, 4017 Mechanical engineering

Abstract:

A miniaturized capacitive pressure sensor has been developed for implantation in the human heart. Since no d.c. current (max 10 μA) can be tolerated inside the heart for safety reasons, an a.c. measuring circuit is mandatory for this purpose. The sensor measures 2 mm × 2 mm and is sealed to a glass substrate by anodic bonding. For the a.c. mode of operation, a capacitive voltage divider and impedance converter have been designed and processed in a standard 3 μm CMOS process. The divider consists of the sensor capacitor and a reference capacitor, and the circuit is powered by an alternating voltage source. The pressure signal modulates the current in the power line. This results in a two-wire approach, with a low output impedance, in total absence of any d.c. components. © 1990.