U.S. Philips Corporation

Gordon A Wilson

Kenneth W Moulding

Jonathan Richard Canning

Jonathan R Canning, Deceased

In order to facilitate its construction as in integrated circuit, the inductive elements of two resonant circuits in a band-pass filter are each constituted by a first port of a respective gyrator circuit (22, 23 and 24, 25 respectively) the second port of which is loaded by a capacitor (3 and 6 respectively). The first ports, across which are connected capacitors (1 and 3 respectively), are connected by a signal path one to the other, as are the second ports, in such manner that a loop is formed comprising the two gyrator circuits and the two signal paths, enabling bilateral coupling of the two gyrator circuits to be obtained by coupling otherwise unused outputs (24+ and 22+) to otherwise unused inputs (22- and 24- respectively) of two-input two-output voltage-controlled current sources (22, 24) which form part of each gyrator circuit.

Pass filter circuit arrangement

In a filter circuit a reactance is simulated by a voltage amplifier the input of which is connected across a reactive element and the output of which is connected in series with that element, thereby enabling, for example, the series arrangement of a pair of inductances to be simulated by a single capacitively-loaded gyrator (15, 16, 7) and a voltage amplifier (15, 8). The circuit shown simulates a series-resonant circuit fed via a series inductor and is suitable for use as a sound trap in a television receiver. A current proportional to the voltage across the unloaded port (8) of the gyrator (15, 16) generates a corresponding voltage across a load resistor (12) and this voltage is injected effectively in series with any voltage present across a pair of input terminals (1, 2) by means of a differential voltage amplifier (13).

Filter circuit arrangement

A circuit has two resonant circuits, each having an active element integrator on the same semiconductor chip. They can therefore have their resonant frequency controlled by the same control signal.

Growing community of inventors

Reigate, United Kingdom

Gordon A Wilson