Ioannis Haritantis

Current differential amplifiers: new circuits and applications

New CMOS current differential amplifiers are proposed suitable for analogue signal processing at high frequencies. They consist of simple current mirrors, which are easy to design and to implement in IC form. Low-voltage low-power design is feasible. Relying on these devices a number of applications are obtained, including lossy and lossless integrators, simulated inductors, active filters, and harmonic oscillators. Theoretical expressions are given for all of the proposed new circuits. The verification of the circuits is also achieved by simulation. Copyright 2001

Log-domain wave filters

A systematic method for designing log-domain wave filters is presented. Wave filters simulate topologically and functionally passive doubly terminated LC ladder prototype filters of low sensitivity. The design in the log-domain is based on a transposition of the signal flow graph (SFG) that corresponds to the wave equivalent of elementary two-port blocks in the linear domain, to the corresponding log-domain SFG. This is achieved by using an appropriate set of complementary operators, in order to preserve the linear operation of the whole circuit. Simulation results of a fifth-order low-pass and a fourth-order bandpass log-domain wave filter are given, using HSPICE. The proposed circuits are suitable for low-voltage operation and in high-frequency applications.

Modular log-domain filters realized using wave port terminators

Log-domain wave filters that simulate the passive LC ladder prototype filters are introduced in this paper. The proposed circuits are constructed from the wave equivalents of the reactive elements corresponding to those in the prototype circuit. The wave equivalent circuits are obtained by using a novel log-domain wave port terminator. The wave equivalent of a capacitor in a shunt branch was chosen as an elementary building block for creating high-order filters. The wave equivalent circuits of all other reactive elements in a shunt or in a series-branch connection can be readily obtained using the elementary building block plus some inverters. This way the derived high-order filter configurations are modular. A design example of a third-order elliptic low-pass filter is given, and the performance of the filter was verified by simulation.

Current-mode differential wave active filters

A technique for obtaining differential active filters suitable for integrated circuit implementation is presented. These filters, based on current-mode differential-wave active blocks, can operate at high frequencies. The cutoff frequency can by tuned by the bias current. The proposed filter topologies are modular and very flexible for both the electronic and the physical design. Simulation results of a third-order elliptic filter, designed in a 0.35-/spl mu/m CMOS technology, are presented.

Development and design of wave SC filters

A direct z-domain simulation of LC ladder and unit-element filters by means of wave SC circuits is presented. the development of a wave SC circuit is achieved by interconnecting a limited number of basic SC building blocks. the derived circuits are fully parasitic-free, symmetric and can be optimally designed for dynamic range maximization and capacitance area minimization. the number of operational amplifiers in the simulated unit-element filters is essentially low in comparison to earlier presented parasitic-insensitive wave SC filters and to leap-frog-type SC filters. Four- and two-phase multiplexed simulated LCR filters can be developed. Bilinear s-z transformation applies for all the circuits; thus the design is exact and there is no requirement for a high clock frequency. Filters with transmission zeros can be developed. the simulated responses of various types of filters are in good agreement with the theory. Detailed examples of different designs are given.

SC bilinear integrators

A different way to develop bilinear integrators is presented. It relies on the inverse recharging technique used in voltage inverter switch (VIS) circuits. Three new circuits, one inverting and two noninverting integrators developed by this technique, are presented. All circuits are parasitic-free without compensation. In two of them, there is no need for component matching to realize the bilinear z-transformation. Consequently the circuits are suitable for integration. The inverting integrator is compared to six known similar circuits. >

Leapfrog-type filters that retain the topology of the prototype ladder filters

New circuit topologies are proposed for obtaining lowpass all-pole and elliptic filters of any order. The derived circuits retain the attractive features of the leapfrog circuits and in addition they retain the topological equivalence with the prototype LC ladders. The formation of transmission zeros is straightforward. An example of 7 th-order elliptic filter including a sensitivity study is given.

A NEW METHOD FOR SC CIRCUIT SYNTHESIS BASED ON THE VOLTAGE INVERSION CONCEPT

A new general method for SC circuit synthesis, based on the voltage inversion concept, is presented. According to the proposed method, first- and second-order SC equivalent admittances are developed and subsequently a number of SC subcircuits are derived. These subcircuits are used in the derivation of high order filters. Emphasis is given to integrator and second-order circuits. All the proposed circuits are fully parasitics free and compare favourably with known circuits. Two design examples of high order filters are also given. One of them was further designed in an IC form.

Modelling of commercially available phase locked loop ICs

A technique is presented for modelling phase locked loop circuits by means of classical analogue electronic circuits. As examples, two models are proposed for corresponding commercially available PLL ICs. These models are suitable for use in various electronic circuit analysis programmes for an accurate and easy design.

High-order switched-capacitor filters realized with one operational amplifier per pole pair

A new switched-capacitor circuit that realizes the general biquadratic transfer function, is proposed. The circuit is exactly equivalent to Fleisher-Laker two-op-amp biquad and maintains its insensitivity to top and bottom plate parasitics without affecting the capacitor area, the capacitor value spread and sensitivity features. It can be cascaded to similar structures for designing high-order circuits. The operational amplifier count is (n/2)+1 for an nth-order circuit. An example of a sixth-order bandpass circuit is given. >