摘要：This paper presents a high precision CMOS opamp suitable for ISFET readout. The opamp is tailored to provide a constant bias condition for ISFET as part of the readout circuits and,hence,is compatible for single chip integration with the sensor. A continuous time auto-zero stabilization technique is studied and employed, with the aim of suppressing the low frequency noises, including the offset voltage, 1/f noise, and temperature drift. The design is based on a 0.35μm CMOS process. With a 3.3V power supply,it maintains a DC open loop gain of more than 100dB and an offset voltage of around 11μV,while the overall power dissipation is only 1.48mW. With this opamp, a pH microsensor is constructed, of which the functionality is verified by experimental tests.

摘要：The accuracy of microwave ranging is mainly limited by the frequency instability of the oscillator that generates the carrier phase signal. A dual transponder carrier ranging method is used to minimize the oscillator noise by combining the reference and the to-and-fro measurements. This ranging approach together with pseudo-noise ranging or other means can be used to measure the inter-satellite distance with a high precision. The pseudo-noise ranging system or other ranging systems help to solve the integer circles while the dual transponder ranging system guarantees the accurate fractional circle. The two satellites work in the master-slave mode. The range measurements are derived on the master satellite while the slave satellite just coherently transfers the received signal, so that the dual transponder ranging system does not need to rely on the time tagging system to synchronize the two satellites. This study first describes the dual transponder carrier ranging system and shows how the system removes most of the oscillator noise components effectively. Then, a detailed design scheme on the frequency planning of the ranging system is presented and the supporting analysis illustrates the feasibility of this system. Based on the design innovation, a laboratory demonstration system is assembled to verify the realizability of the dual transponder ranging system. The experimental results demonstrate that a high level of accuracy (about 30 μm under laboratory circumstance) can be achieved by the use of the proposed dual transponder carrier ranging system.