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The paper introduces a novel sinusoidal quadrature oscillator (QO) with low harmonic distortion. The oscillator utilizes the non-linear non-inertial principle for amplitude stabilization and thus a fast transition to 0 steady state oscillations should be accomplished. This feature makes the QO suitable for operation at very low frequencies. The oscillator(More)
This contribution deals with an application of three different algorithms which optimize a group delay of analog filters. One of them is a part of the professional circuit simulator Micro Cap 7 and the others two original algorithms are developed in the MATLAB environment. An all-pass network is used to optimize the group delay of an arbitrary analog(More)
OBJECTIVE According to recent findings neuroendocrine response related to dissociative symptoms is related to dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis but HPA axis functioning as related to dissociation is only partially understood. METHOD With the aim to test the relationship between basal serum cortisol and dissociative symptoms(More)
  • Karel Hajek
  • Proceedings of 21st International Conference…
  • 2011
The design of high-voltage wideband amplifiers for excitation of ultrasonic actuators and transmitters has problem with limited slew-rate for full range excitation. This problem is connected with value of total power dissipation of transistors, especially for the advantageous class B stage with common emitters. The power dissipation of transistor is(More)
The voltage noise of preamplifiers limits a sensitivity of many systems in the case of the low value of an internal resistance of a signal source. The offset and 1/f noise as a special case of this noise can be reduced by some variant of chopping technique as it is known for DC amplifiers. This idea is used for new principle of reducing of the white voltage(More)
It is necessary to improve the analog preprocessing dynamic range. Special problem consists in minimisation of the noise and offset. The use of a tunable low-pass filter brings usually problems with increasing of the offset and drift. The survey of standard solutions of these problems is shown and new solution of this problem too. This new way consists in(More)
In this paper, we present two biquadratic structures for cascade filter design, which are intended to provide high attenuation rate in the stopband area of frequency transfer characteristic. The filters optimized in this way can reach better electrical performances, such as higher maximal cut-off frequency or dynamic range, even with conventional (low power(More)
Quartz crystal microbalance (QCM) is a high sensitive chemical sensor which has found widespread spectrum of applications. There are several mechanisms that are related to fluctuation phenomena. Since the aim of our research is oriented to study the sensitivity and influence of different kind of noises on sensor resolution, we modified an existing method to(More)
The non-linear electro-ultrasonic spectroscopy was used as a non-destructive testing method for the polymer based and cermet thick film resistors evaluation. We carried out the correlation between this method and standard testing methods as noise spectroscopy and the third harmonic voltage measurements. The measuring set-up with the ultrasonic transducer(More)