Abstract
This paper presents a new concept of a capacitance multiplier using the topology of differential voltage buffer and current conveyor, where the capacitor is connected to the current input terminal. The presented topology overcomes the typical issue known from similar solutions, i.e. creation of an undesired lossy character of the impedance plot. The added feedback path in the structure serves for minimization of the serial parasitic resistance of the current input terminal as well as the output resistance of differential voltage buffer. The electronic driving of the current and voltage internal gains of the active elements allows the adjustment of the capacitance multiplication factor as well as readjustment of the overall capacitance structure between the lossy and lossless modes of operation. The adjustment of the multiplication factor intentionally targets low ranges of gains. Despite that the multiplication factor equals or is less than 1, the range of adjustability is very wide. Simple modifications of the proposed concept leading to the differential-mode operation and enhancement of the multiplication factor are shown and explored. They were experimentally tested in more than 2 decades, from 0.03 to 5.8 nF, and controlled by single DC voltage from 0.1 to 1.0 V. The outputs of experimental measurements meet with the PSpice simulations and confirm the design validity.
Highlights
Electronically adjustable and tunable circuit applications are receiving a lot of attention in the fields of signal generation and signal processing
Such a high value of capacity is obtained as a product of a small value of capacity and a quite large constant [3]
The upper limits of MF are given by the gain limits of the active circuitry
Summary
Adjustable and tunable circuit applications are receiving a lot of attention in the fields of signal generation and signal processing. We can summarize most important benefits of the newly presented approach to the following points: 1) Electronic adjustment of the MF influencing the value of the equivalent capacity, 2) Low current gain control (attenuation ) used for electronic adjustment (causing negligible increase of the power consumption), 3) A wide range of adjustability and tunability for low gain ranges, 4) Eliminated parasitic effects of structures using a floating capacitor, 5) A simple electronic elimination of the lossy part (zero frequency) of the frequency response in the impedance plot by adjustment of another electronically controllable parameter, 6) Possible implementation of the floating capacitance multiplier, when additional terminals of AEs are added, 7) A simple option to extend the topology by additional elements of the same type in order to obtain even more extended range of electronic tuning of the equivalent capacity.
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