Low-Sensitivity Active RC-filter of the Second Order with an Extended Frequency Range

 
Denisenko D.Yu. (Don State Technical University), Prokopenko N.N. (Don State Technical University, IPPM RAS)
 
Abstract - At present, the theory of RC-filters is most actively developing in the direction of tunable filters, filters on switched capacitors, and also the use of new types of active elements, including multi-differential operational amplifiers, various modifications of current conveyors. The search for architectures that minimize the effect of the areas of amplification of active elements on the main parameters of the active RC-filter continues. However, not all the new active elements, which today number more than 150 variants, are available in the form of serial microcircuits. At the same time, classic operational amplifiers are produced in large numbers, including in the uncompact version for "systems in the case". Operational amplifiers are the most common active elements. So on the international market of microelectronic products more than 2 000 names of operational amplifiers are presented. In this connection, the search for new architectures of the active RC-filter on operational amplifiers is still of interest. It should also be noted that in many cases, the architectures of active RC filters on operational amplifiers can be successfully implemented in the basis of new active elements. The paper proposes a new structure of a universal low-sensitivity active RC-filter of the second order with an extended frequency range. The active RC-filter circuit is implemented on three operational amplifiers and is recommended for use as a universal link in the construction of bandpass filters, as well as low and high frequency filters. It is shown that, due to the introduction of a single new connection in the circuit of the known KHN-filter in the transfer function of the active RC-filter under consideration, additional coefficients appear that depend on the amplification areas of the operational amplifiers. In the final analysis, this reduces the influence of the frequency characteristics of operational amplifiers on the characteristics being realized. Computer simulation of the proposed active RC-filter showed that for the case of a bandpass filter the frequency range of operation is approximately 1.5 times greater than in the widely used KHN-filter. And this effect is achieved without the introduction of any additional active and passive elements. In this case, the relative gain on the frequency range will be the higher, the smaller the amplification area of the operational amplifiers used. In the investigated filter scheme, micro-power operational amplifiers can be used, which allows recommending its use in low-temperature analog-to-digital interfaces.

Keywords - universal active RC-filter, bandpass filter, operational amplifier, the effect of gain area, frequency characteristics, frequency range, KHN-filter

Низкочувствительный активный RC-фильтр второго порядка с расширенным частотным диапазоном

 
Денисенко Д.Ю. (Донской государственный технический университет, г. Шахты), Прокопенко Н.Н. (Донской государственный технический университет, Институт проблем проектирования в микроэлектронике РАН, г. Шахты)
 
Аннотация - Предлагается новая структура низкочувствительного активного RC-фильтра второго порядка (ARCф) с расширенным частотным диапазоном. Схема ARCф реализуется на трех операционных усилителях (ОУ) и рекомендуется для использования в качестве универсального звена при построении полосовых фильтров, а также фильтров нижних и верхних частот. Показано, что благодаря введению новой связи в передаточной функции рассматриваемого ARCф появляются дополнительные разностные коэффициенты, зависящие от площадей усиления ОУ, что позволяет снизить влияние частотных свойств ОУ на реализуемые характеристики.

Ключевые слова - универсальный активный RC-фильтр, полосовой фильтр, операционный усилитель, влияние площади усиления, частотные характеристики, частотный диапазон, KHN-фильтр.