Digitally-programmable filters have been an ongoing research topic for a number of years. The first such filters were FIR transversal filters using Charge-Coupled Devices (CCD's) and IIR recursive filters using switched-capacitor (SC) techniques. Although both techniques achieve excellent results, they require non-standard and/or additional IC fabrication steps. Low substrate doping...
It has become customary in electrical engineering to think of
signal processing in terms of voltage variables to the exclusion of
current variables. This tendency has resulted in voltage signal
processing circuits such as voltage-controlled voltage sources
(VCVS) and voltage-mode operational amplifiers. However, the VCVS
operational amplifier has several limitations...
With increasing interest in current-mode analogue processing due to its high
performance properties such as speed, bandwidth and accuracy compared to voltage-mode
processing, new current-mode alternatives to various conventional circuit designs are
appearing. In this report, a novel circuit design to construct a fully-differential current-mode
operational amplifier ( OP-AMP )...
In this dissertation, two important current mode circuit design subjects have
been explored. In the first part, the switched-current circuit technique has been
investigated. The fundamental performance and limitations of this technique are
explored. One of the major limitations, the signal distortion caused by clock
feedthrough has been substantially reduced...
In this paper, an analysis of the clock-feedthrough effects in
switched-current (SI)' circuits will be presented. The clock-feedthrough
effects caused by the non-ideal characteristic of MOS
switches when they are turned off limit the accuracy of the analog
track-and-hold (T/H) circuits. A model to analyze and characterize this
effect is...
The design and implementation of Switched-Current (SI) ladder filters is
described. SI filters require only a standard digital CMOS process and the power
supply voltage requirement is low. SI circuits also can be potentially operated at
higher frequencies than Switched-Capacitor (SC) filters due to the low-impedance
wideband nodes of the...
Clock-feedthrough effects, channel-length modulation and device mismatch are
the main causes of the inaccuracy of Switched-Current (SI) circuits. In this paper, these
non-ideal effects are analyzed. A high-performance current mirror, namely regulated
cascode current mirror, which eliminates drain voltage variation problem is introduced.
By using this current mirror as a...
The semiconductor gallium arsenide (GaAs) has many potential
advantages over the more widely used semiconductor silicon (Si).
These include higher low field mobility, semi-insulating substrates,
a direct band-gap, and greater radiation hardness. All these
advantages offer distinct opportunities for implementation of new
circuit functions or extension of the operating conditions...