Zdenek Kincl

Parametric reduction of Jacobian matrix for fault analysis

The paper deals with a fast numerical method for generating the Jacobian matrix of network function for large analog linear circuits. It is based on the use of cofactor matrices. The computational cost of the Jacobian is comparable to the cost of computing a single network function on selected frequencies. In addition, the method allows performing the reduction of Jacobian matrix based on large-change sensitivities in order to decrease the computational complexity of subsequent testability analysis. An example analysis of a frequency filter is presented.

Parametric fault diagnosis using overdetermined system of fault equations

The paper shows a procedure for testing linear analog circuits using multi-frequency parametric fault diagnosis. Some methods for test frequency selection determine the total number of test frequencies equal to the total number of tested network parameters. The error between actual and estimated network parameters is evaluated only on several frequencies while the rest of the frequency band of the circuit is not taken into account. A new approach based on an overdetermined system of fault equations which can dramatically reduce the total error of the solution is presented. A practical example of application is shown on the test frequency selection of an EMI filter.

Study of practical problems in two-loop CCTA based biquad: Finite attenuations in stop bands

Quite neglected and underlying problem of modern active functional blocks is presented and demonstrated in this contribution on a current-mode active filter. The discussed problem is an undesirable transfer in stop band of multifunctional frequency filters. It is caused by several occasions related to small-signal parameters of active elements (impedance levels) in the circuit. In some cases it leads to parasitic feedback and undesirable transfers in circuit. Problems are discussed on example with KHN-type filter where quite novel active element known as Current Conveyor Transconductance Amplifier (CCTA) is used.

Tunable oscillator derived from Colpitts structure with simply controllable condition of oscillation and synthetic inductor based on current amplifier and voltage differencing transconductance amplifier

Our contribution discusses modification of well-known Colpitts LC oscillator to fully electronically controllable type utilizing adjustable current amplifier and inductance simulator based on voltage differencing transconductance amplifier (VDTA) instead of common bipolar transistor and passive metal coil. Implementation of current amplifier allows independent and direct control of oscillation condition, simplifies design (capacitors can have equal values because condition is not dependent on them) and used inductance equivalent based on VDTA allows linear control of frequency of oscillation and quadrature outputs with unchangeable amplitudes during the tuning process. Theory was verified by PSpice simulations and experimental measurement.