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Negative Conductive Circuit

IP.com Disclosure Number: IPCOM000077114D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Croisier, A: AUTHOR

Abstract

In many cases, it is necessary to compensate for network losses. Such a compensation can be advantageously made through a negative conductance circuit. By negative conductance, one usually means a negative impedance element which is short-circuit stable.

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Negative Conductive Circuit

In many cases, it is necessary to compensate for network losses. Such a compensation can be advantageously made through a negative conductance circuit. By negative conductance, one usually means a negative impedance element which is short-circuit stable.

The figure shows such an element with one connection grounded. Such an element can obviously not be coupled through a capacitor to the remaining circuit, since this would mean instability at DC. It is, therefore, desirable to have DC coupled negative conductances.

In some applications however, the DC potential of the point of connection is not known. In this case, a negative conductance which would operate at DC would supply an unknown current to the circuit and this may be undesirable.

The negative conductance circuit shown does not supply any current at DC. In other words, its effect disappears at DC, yet it remains short-circuit stable.

The circuit shown makes use of an operational amplifier, three resistors and a capacitor. A second capacitor (C2) may be added to suppress the negative resistance action at high frequencies. The analysis of this circuit gives: V1 - V0 = V0R2/(R1 + 1 over j omega C1) 10 = -(V1-V0)/R3 Z0 = V0/10 = R3 over R2 (-R1 - 1 over j omega C1) = RN - 1 over j omega CN.

The circuit impedance appears as a negative resistance in series with a negative capacitance.

If RL is a resistance connected between V0 and ground, and if we consider negative and positive feedba...