A new analogue circuit design methodology using independently optimised self-cascode (SC) structures is proposed. Based on the concept of the dual-workfunction-gate structures, which are equivalent to SC structures, transconductance and output resistance optimised SC MOSFETs were used in the differential input and output stages, respectively. An operational amplifier (opamp) with the proposed design methodology using standard 0.18 µm CMOS technology was designed to provide better performance. The measured DC gain of the fabricated opamp with independently-optimised SC MOSFETs was approximately 12 dB higher than that of the conventional opamp.
A unified potentiostat circuit for both O 2 -and H 2 O 2 -based electrochemical glucose sensors was proposed and its function was verified by circuit simulations and measurement results of a fabricated chip. This circuit consisted of an operational amplifier, a comparator and current mirrors. The proposed circuit was fabricated with a 0.13 ㎛ thick oxide CMOS process and an active area of 360 ㎛ × 100 ㎛. The measurements revealed an input operation range from 0.5 V to 1.6 V in the H 2 O 2 -based bio-sensor and from 1.7 V to 2.6 V in the O 2 -based bio-sensor with a supply voltage of 3.3 V. The evaluation results showed that the proposed potentiostat circuit is suitable for measuring the electrochemical cell currents of both O 2 -and H 2 O 2 -based glucose sensors.
This paper presents a design and fabrication of 0.5 V two stage operational amplifier. The proposed operational amplifier utilizes body-driven differential input stage and self-cascode current mirror structure. Cadence Virtuoso is used for layout and the layout data is verified by LVS through Mentor Calibre. The proposed two stage operational amplifier is fabricated using 0.13 ㎛ CMOS process and operation at 0.5 V is confirmed. Measured low frequency small signal gain of operational amplifier is 50 ㏈, power consumption is 29 ㎼ and chip area is 75 ㎛ × 90 ㎛.
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