Active inductor

An active inductor circuit comprising:

• first and second inductor terminals for coupling to respective external terminals, said first and second inductor terminals being coupled to a first transconductance circuit;
• a second transconductance circuit;
• a feedback circuit;
• an output terminal of said first transconductance circuit being coupled to an input terminal of said second transconductance circuit;
• an output terminal of said second transconductance circuit being coupled to an input terminal of said first transconductance circuit via said feedback circuit;
• and
• a capacitor coupled between said output terminal of said first transconductance circuit and said second inductor terminal,
• wherein said first transconductance circuit includes an inverter, a first resistor, and a second resistor, and
• wherein said second transconductance circuit includes an active device in series with a third resistor.

An active inductor circuit comprising:

• first and second inductor terminals for coupling to respective external terminals, said first and second inductor terminals being coupled to a first transconductance circuit;
• a second transconductance circuit;
• a feedback circuit;
• an output terminal of said first transconductance circuit being coupled to an input terminal of said second transconductance circuit;
• an output terminal of said second transconductance circuit being coupled to an input terminal of said first transconductance circuit via said feedback circuit;
• and
• a capacitor coupled between said output terminal of said first transconductance circuit and said second inductor terminal,
• wherein the feedback circuit linearises the relationship between a synthesised DC voltage between said first and second terminals and a DC output current through said second transconductance circuit.

An active inductor circuit comprising:

• first and second inductor terminals for coupling to respective external terminals, said first and second inductor terminals being coupled to a first transconductance circuit;
• a second transconductance circuit;
• a feedback circuit;
• an output terminal of said first transconductance circuit being coupled to an input terminal of said second transconductance circuit;
• an output terminal of said second transconductance circuit being coupled to an input terminal of said first transconductance circuit via said feedback circuit;
• and
• a capacitor coupled between said output terminal of said first transconductance circuit and said second inductor terminal,
• wherein the current through said second transconductance circuit is at least a factor 100 larger than the current through said first transconductance circuit and through said feedback circuit.

An active inductor circuit comprising:

• first and second inductor terminals for coupling to respective external terminals, said first and second inductor terminals being coupled to a first transconductance circuit;
• a second transconductance circuit;
• a feedback circuit;
• an output terminal of said first transconductance circuit being coupled to an input terminal of said second transconductance circuit;
• an output terminal of said second transconductance circuit being coupled to an input terminal of said first transconductance circuit via said feedback circuit;
• and
• a capacitor coupled between said output terminal of said first transconductance circuit and said second inductor terminal,
• wherein the equivalent inductance equals the capacitance value of said first capacitor divided by the product of the transconductance values of said first transconductance circuit and said second transconductance circuit.