Abstract
This paper presents a simple relaxation generator, suitable for a sensor interface, operating as a transducer of capacitance to frequency/period. The proposed circuit employs a current feedback operational amplifier, fabricated in I3T25 0.35 m ON Semiconductor CMOS process, and four passive elements including a grounded capacitor (the sensed parameter). It offers a low-impedance voltage output of the generated square wave. Additional frequency to DC voltage converter offers output information in the form of voltage. The experimental capacitance variation from 6.8 nF to 100 nF yields voltage change in the range from 21 mV to 106 mV with error below 5% and sensitivity 0.912 mV/nF evaluated over the full range of change. These values are in good agreement with simulation results obtained from the Mathcad model of frequency to DC voltage transducer passive circuit.
Highlights
Electrical sensors form an important part of complex electronic systems, which are used in many fields [1]. They are required for transformation of various physical quantities to measurable information in the form of an electrical signal
The capacitance to frequency transducer has been extended in order to obtain DC voltage by a simple passive converter
Due to requirements on the simplicity and very low-power consumption, in this work we have used our previously developed IC device consisting of CCII and voltage buffer cells [38]
Summary
Electrical sensors form an important part of complex electronic systems, which are used in many fields (e.g., industry, healthcare, consumer electronics and wireless communications) [1]. Differential methods, in comparison with relaxation generator-based approaches, offer higher accuracy and low measurement error (units of percent) These solutions [15,16] are complex. Principles in the above-discussed papers are totally different from our simple analog proposal (a circuit generates an autonomous waveform) and all the described methods require additional control logic, external clock signal, synchronism and switching accessory. Their overall complexity (mixed analog-digital design) and power consumption are significantly higher than our simple analog proposal
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