2024-03-29T07:56:15Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/848302016-02-17T16:06:53Zcom_10261_90com_10261_4col_10261_343
00925njm 22002777a 4500
dc
Rodríguez-Vázquez, Ángel
author
Domínguez-Castro, R.
author
Medeiro, Fernando
author
Delgado-Restituto, Manuel
author
1995-03
This paper uses fundamental models to derive design conditions for maximum speed and resolution in CMOS transimpedance comparators. We distinguish two basic comparator architectures depending on whether the input sensing node is resistive or capacitive, and show that each type yields advantages for different ranges of input current. Then, we introduce a class of current comparator structures which use nonlinear sensing and/or feedback to combine the advantages of capacitive-input and resistive-input architectures. Two members of this class are presented demonstrating resolution levels (measured on silicon prototypes) in the range of pAs. They exhibit complementary functional features: one, the current steering comparator, displays better transient response in the very comparison function, while operation of the other, the current switch comparator, is easily extended to support systematic generation of nonlinear transfer functions in current domain. The paper explores also this latter extension, and presents current-mode circuit blocks for systematic generation of nonlinear functions based on piecewise-linear (PWL) approximation. Proposals made in the paper are demonstrated via CMOS prototypes in two single-poly CMOS n-well technologies: 2μm and 1.6μm. These prototypes show measured input current comparison range of 140 dB, resolution and offset below 10 pA, and operation speed two orders of magnitude better than that of conventional resistive-input circuits. Also, measurements from the PWL prototypes show excellent rectification properties (down to a few pAs) and small linearity errors (down to 0.13%).
Analog Integrated Circuits and Signal Processing 7(2): 149-165 (1995)
0925-1030
http://hdl.handle.net/10261/84830
10.1007/BF01239169
1573-1979
High resolution CMOS current comparators: design and applications to current-mode function generation