Arrangements for simulating inductance and filter networks incorporating such improvements
AssigneeThe Post Office
InventorsJohn Mortimer Rollett, David Richard Wise
Life of this patent
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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.
Claims7
In a filter network a circuit arrangement comprising a first and second amplifier element each having an overall gain substantially equal to unity and each having a single input and a single output interconnected by way of a first and a second series network respectively, each series network including a resistive impedance element and a capacitive impedance element and a first junction point between said resistive and said capacitive impedance elements and wherein the product of the values or resistance and capacitance of the elements in the series network for each of said first and second amplifiers is equal, a first non-inductive coupling element interconnecting the series networks of the first and second amplifiers, the circuit arrangement being a symmetrical mirror image in terms of components about said first non-inductive coupling element.
Dependencies are inferred from the claim text.