Approximating principle-based unconventional converter for force measuring

This paper deals with approximating principle-based converters for force measurement. Our task was to design a circuit in which a elimination of a flicker noise follows from its functional principle; no other special circuits were used to achieve this goal. A modified flip-flop circuit is the main part of the proposed system, inside of which switched capacitors replace classical load resistors. The principle of the measurement lies in the fact that a measured force changes the values of the switched capacitors. The flip-flop asymmetry is then compensated by a deviation in the controlling frequencies of these switched capacitors. The circuit differs from the classical approximating converter in that it is not voltage but frequency approximation. The choice was frequency, because generated signals of a crystal oscillator have a very high stable frequency and in the process of approximation all sub-frequencies are generated from it. The circuit was simulated with the TSPICE, VerilogA and SPECTRA Cadence simulator with respect to its realization in CMOS 0.8 μm technology. The results of simulations which were in agreement when compared to the theoretical results are reported.