Abstract: The invention relates to electrical oscillators arranged to oscillate so as to produce a substantially sinusoidal output signal. The said oscillator includes a general impedance transvertor circuit arrangement having two differential amplifiers connected only to a plurality of resistive and capacitive impedance elements and arranged to simulate a tuned circuit with sufficient feedback to maintain oscillation within the tuned circuit. The transvertor circuit is an active device in the form of an impedance invertor circuit or a convertor circuit.

Abstract: The invention relates to electrical oscillators arranged to oscillate so as to produce a substantially sinusoidal output signal. The said oscillator includes a general impedance transvertor circuit arrangement having two differential amplifiers connected only to a plurality of resistive and capacitive impedance elements and arranged to simulate a tuned circuit with sufficient feedback to maintain oscillation within the tuned circuit. The transvertor circuit is an active device in the form of an impedance invertor circuit or a convertor circuit.

Abstract: An active network incorporating a gyrator, having a first and a second operational amplifier each said operational amplifier having an inverting input and a non-inverting input, the inverting inputs of said first and said second operational amplifiers being directly connected, and wherein the outputs of said first and said second operational amplifiers are resistively connected to the inverting inputs of said operational amplifiers, an input terminal is connected to said non-inverting input of said first operational amplifier which said input terminal is connected resistively to said output of said second operational amplifier, said output of said first operational amplifier is capacitively coupled to said non-inverting input of said second operational amplifier and said non-inverting input of said second operational amplifier is resistively connected to earth.

Abstract: This invention concerns gyrator circuits, and particularly gyrator circuits used in filters. The gyrator network contains two differential input operational amplifiers and an input network, some of the elements of which are variable to enable the Q, the bandwidth and the resonant frequency to be adjusted in such a way that previously adjusted parameters are not changed. The circuit may have three configurations according to the position of a pair of ganged switches, alternatively the switches may be replaced by fixed links.

Abstract: A filter network particularly suitable for construction in micro-electronic circuitry for application in telephony systems is formed by simulating inductance in a circuit arrangement incorporating only resistance, capacitance and amplifying elements. The symmetry of the circuit arrangement and coupling into the filter network simplifies fabrication and reduces the number of amplifiers previously required to perform similar filter functions. The filter networks may be built up by coupling a chain of circuit arrangements each including two unity gain amplifiers having a series resistor/capacitor feedback network and a non-inductive element interconnecting the two amplifier feedback networks.