SU481120A1 - Active - low pass filter - Google Patents

Description

one

The invention relates to electrical engineering and can be applied in communication technology, measurement technology, automation, etc.

An active low-pass C filter is known, containing a series-connected integrating and inertial link, made on operational amplifiers and covered by a loop of common negative feedback.

The scheme of the known active KS filter is complex, since it contains, in addition to the functionally necessary elements of the integrating and inertial link, an additional inverting link used exclusively to form the corresponding phasing of net feedback.

The purpose of the invention is to simplify the filter. This is achieved by the fact that the non-inverting inputs of the operational amplifiers are connected to a tap of a resistive voltage divider connected at the output of the filter.

The drawing shows a schematic diagram of the proposed active / C-filter lower) their frequencies.

The scheme contains consistently integrated 1 and inertial 2 units. To their common point 3, a resistive voltage divider 4 is connected, one of the arms 5 of which forms a loop of common negative feedback.

The proposed active / C-filter works as follows.

At low frequencies, where the time constants of links 1 and 2 are small, the scheme is covered by one hundred percent positive feedback of a consistent type. The feedback voltage is applied to the zero point of 3 links 1,2c of the divider 4, the length of which 5 forms the specified loop. Therefore, the input coherence of the circuit is large, and the transfer coefficient is constant and determined by the division factor of divider 4. As its frequency becomes comparable to the time of links 1 and 2 as the frequency increases, the gain in the overall feedback loop decreases, which leads to an increase in filter transmission coefficient. At high frequencies, where the time of links 1 and 2 is much longer than the period of the operating frequency, the signal is completely attenuated in links x and does not reach the output of the filter, therefore the transmission coefficient is close to zero.

Subject invention

An active C-low-pass filter containing a series-connected integrating and inertial link, made 30 on operational amplifiers and covered

a loop of a common negative connection oopaTiioii, characterized in that, in order to make the filter more efficient, the non-sig- nating inputs of the amplifiers are connected to a tap of a resistive delntel switch connected to the output of the filter.

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