Design of VCVS multifeedback active filters from 2nd to 8th order using one operational amplifier

In 1955, Sallen and Key presented a method of designing RC active filters. A catalogue of 2nd- and 1st-order active networks has been given that enabled the designer to achieve thespecified transfer function by cascading the suitable 2nd- and 1st-order building blocks. In 1969, Shepard presented another method of designing RC active filters. A catalogue of 3rd- and 2nd-order active networks, with unity gain (K=1), were given which enabled the designer to achieve the specified transfer function by cascading the suitable 3rd and 2nd-order building blocks. In this Thesis we designed active filters from 2nd- to 8th-order active filters using in each case only one op amp in order to reduce the number of active elements. All resistances will be taken equal to each other, which is attractive from a practical point of view (integration). We have found that a voltage gain larger than unity will decrease the spread of the element values considerably. Further, we found it advantageous to choose two of the capacitances equal to each other (ck+1 = Ck). These choices lead to lower capacitances ratios and it is found that an adjustable voltage gain facilitates, if necessary, a precise adjustment of the filter characteristics. A method was also presented to realize high-pass, band-pass and band-stop functions. Design data table for normalized Butterworth, Chebyshev (0.1, 0.5, 1, 2 and 3 dB ripple) and Bessel filters and example was included for 2nd- to 8th-order filters. Visual feedback of sound is useful as a training aid to help speech impediments such as stuttering and some forms of mental retardation. We divided the audio into many narrow channels using active filters. The energy in each channel is detected and used to control a LED

A quick design for a fifth-order VCVS active filter using one op.-amp.

To realize a fifth-order VCVS active filter three filters are usually employed in cascade connection, one of first-order and two second-order filters. In this paper, we prove that the number of active elements can be reduced down to one if we use a fifth order filter with one operational amplifier (op.-amp.). Also, a voltage gain K larger than unity (K as a free parameter) decreases the spread element values considerably. Design data tables for normalized Butterworth, Chebyshev and Bessel VCVS filters and LP, HP, BP and BS examples are included. © 1998 Taylor and Francis Group, LLC

Ovarian hyperstimulation syndrome (OHSS): diagnosis and management

Objective: To present our experience and the current knowledge about pathophysiology, diagnosis, and management of the ovarian hyperstimulation syndrome (OHSS). Design: Retrospective study concerning clinical and laboratory findings of severe OHSS. Setting: General ICU at a maternity-surgical hospital. Patients: Ten patients suffering from severe OHSS. Interventions: Supportive and preventive therapeutic measures applied are described. Measurements and results: Admission and discharge data as well as worst values during disease course were recorded. Clinical and laboratory findings showed third space fluid shift leading to weight gain, generalized tissue edema, ascites, hydrothorax, abdominal distension and pain, chest discomfort, hypovolemia, dehydration, ovaries enlargement, electrolyte disturbances, hypoalbuminemia, high hematocrit, urea, and WBC. Conclusions: OHSS is an iatrogenic complication of assisted conception of unknown pathogenesis, with potentially life-threatening sequelae due to hemoconcentration such as circulatory shock, ARDS, hepatorenal failure, thromboembolic phenomena, and multi-organ dysfunction syndrome. Gynecologists and intensivists must be aware of the diagnosis and management of the syndrome because of the widely used reproductive techniques for assisted conception