ACTIVE INDUCTOR

Abstract

The present invention provides an active inductor that includes an active all-pass type 90° phase advancing circuit comprising an operational amplifier, a first resistor connected between an inversion input end of the operational amplifier and an input terminal, a capacitor connected between a non-inversion input end of the operational amplifier and the input terminal, a second resistor connected between an output end of the operational amplifier and the non-inversion input end, and a third resistor connected between the non-inversion input end and a ground point; and a fourth resistor having a resistance value sufficiently lower than respective resistance values of the first through third resistors connected between input and output terminals of the active all-pass type 90° phase advancing circuit and an impedance value of the capacitor. Thus, an equivalent inductor is obtained between the input terminal and the ground point.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, wherein like reference numerals identify like elements in which:

FIG. 1 shows a first embodiment of an active inductor according to the present invention and is a circuit diagram showing a circuit configuration thereof; and

FIG. 2 shows a second embodiment of an active inductor according to the present invention and is a circuit diagram showing a circuit configuration thereof.

Claims

1. An active inductor comprising: input terminals;an active all-pass type 90° phase advancing circuit comprising an operational amplifier, a first resistor connected between an inversion input end of the operational amplifier and the corresponding input terminal, a capacitor connected between a non-inversion input end of the operational amplifier and the input terminal, a second resistor connected between an output end of the operational amplifier and the inversion input end, and a third resistor connected between the non-inversion input end of the operational amplifier and a ground point; anda fourth resistor having a resistance value sufficiently lower than respective resistance values of the first through third resistors connected between input and output terminals of the active all-pass type 90° phase advancing circuit and an impedance value of the capacitor,whereby an equivalent inductor is obtained between the input terminal and the ground point.

2. An active inductor comprising: input terminals;an active all-pass type 90° phase advancing circuit comprising an operational amplifier, a first resistor connected between an inversion input end of the operational amplifier and the corresponding input terminal, a second resistor connected between a non-inversion input end of the operational amplifier and the input terminal, a third resistor connected between an output end of the operational amplifier and the inversion input end, and an inductor connected between the non-inversion input end of the operational amplifier and a ground point; anda fourth resistor having a resistance value sufficiently lower than respective resistance values of the first through third resistors connected between input and output terminals of the active all-pass type 90° phase advancing circuit and an impedance value of the inductor,whereby an equivalent inductor is obtained between the input terminal and the ground point.