An area-variable MOS varicap and its application in programmable TAP weighting of CCD transversal filters

Abstract

T. i , , and J(n) are functions of position, 0 < X < L . The coefficients J(m) are derivatives of the intrinsic 'diode characteristic at Y = V, (8). REFERENCES[ 11 M. Wolf, "Limitations and possibilities for improvement of photovoltaic solar energy converters,"Proc. IRE, vol. 48, p. 1246IRE, vol. 48, p. , 1960 [ 21 J. J. Wysocki, "The effect of series resistance on photovoltaic solar energy conversion," RCA Rev., vol. 22, p. 57, 1961. [3] R. J. Handy, "Theoretical analysis of the series resistance of a solar cell," Solid-State Electron., vol. 10, p. 765, 1967. [4] J. L. Boone and T. P. Van Doren, "Solar-cell design based on a distributed diode analysis," IEEE Trans. Electron Devices, vol. ED-25, p. 767, 1978 A. B. BHATTACHARYYA AND HANS W A L L I N G AAbstract-A new three-terminal MOS varicap is proposed where the terminal capacitors are made voltage variable not by the modulation of depletion width but by changing the area of inversion under the gate. An MOS capacitor realized on silicon with an impurity gradient along the surface provides the control on the area of inversion because the gate threshold voltage is determined by the doping concentration at the surface.The inhomogeneous doping along the surface is implemented making use of the lateral diffusion from a doped oxide surface. Fabrication details of the capacitor compatible with n-channel silicon gate technology are presented. The C-V relationship for the terminal capacitors is simulated by a piecewise model and agreement with measured results is shown.The Area-Variable MOS Varicap (AVMOSV) is used in implementing an electrically programmable CCD filter with variable TAP weighting. Computer simulation shows considerable promise of area-variable capacitors in TAP weight control and transversal filter realization. Preliminary performance characteristics of a programmable CCD filter are presented.

Analog integrated filters or continuous-time filters for LSI and VLSI

“…In the implementation (an integrator), the gate as well as the back bias are controlled by half the signal voltage superimposed on the bias voltage (see also [33]). Elimination of all even-order harmonics is also obtained when the symmetric integrators in figure 22 (see [34]) are used.…”

“…Depletion layers in diffused monolithic or in poly silicon electrodes may be the cause of increased voltage dependence (when they are not sufficiently highly doped). Depletion layers may also be applied on purpose to make voltage variable capacitors (see, for example, [22]).…”