Synthetic circuit component and amplifier applications

• US 6,879,215 B1
• Filed: 05/10/2002
• Issued: 04/12/2005
• Est. Priority Date: 05/10/2002
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Roach, Steven D.
• Primary Examiner(s): Nguyen, Khanh V.
• Application Number:
  US10/144,160
• Time in Patent Office: 1,068 Days
• Field of Search: 330/76, 330/292, 330/307, 330/156, 4 7/6
• US Class Current: 330/292
• CPC Class Codes: H03F 1/08 Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements wide-band amplifiers with inter-stage coupling networks incorporating these impedances H03F1/42
• CPC Class Codes: H03F 1/14 by use of neutralising means
• CPC Class Codes: H03F 2200/36 the amplifier comprising means for increasing the bandwidth
• CPC Class Codes: H03F 3/195 in integrated circuits

Abstract

Synthetic circuit elements and amplifier applications for synthetic circuit elements are provided. The synthetic circuit elements disclosed herein may be configured to compensate for some or all of the parasitic capacitance normally associated with circuit elements disposed on a substrate providing a selectable impedance characteristic. Amplifier circuit constructed using such synthetic circuit elements exhibit improved performance characteristics such as improved recovery time, frequency response, and time domain response.

Claims

1. In an integrated circuit, a method for providing a synthetic circuit component with a variable impedance characteristic comprising:

providing a resistive circuit element disposed on the integrated circuit, wherein a distributed parasitic capacitance exists between the resistive element and a conductor, and the conductor is also disposed on the integrated circuit;

coupling an output of an amplifier circuit to the conductor; and

applying a drive signal from the amplifier circuit to the conductor to vary the amount of distributed parasitic capacitance experienced by the resistive circuit element and thereby vary the impedance of the synthetic circuit element.

2. The method of claim 1 wherein the applying further comprises varying the gain of the amplifier circuit to vary the magnitude of the drive signal to obtain a desired impedance characteristic.

3. The method of claim 1 further comprising applying a signal to the input of the amplifier circuit that is proportional a signal applied to the resistive circuit element.

4. The method of claim 1 wherein the providing further comprises providing a plurality of conductors and wherein the resistive circuit element has a distributed parasitic capacitance to at least some of the plurality of conductors.

5. The method of claim 4 wherein the plurality of conductors includes at least one semiconductor well segment.

6. A method for improving a time domain response of an amplifier circuit so that the amplifier circuit accurately replicates digital signals without suffering from significant amplitude deterioration, the method comprising:

coupling a coupling capacitor to a synthetic circuit component and an amplifier, wherein the synthetic circuit component comprises a conductor and a resistive element, the conductor and the resistive element are coupled together;

coupling a bootstrap amplifier to the coupling capacitor and the synthetic circuit component; and

the bootstrap amplifier providing a drive signal to the synthetic circuit component derived from a signal applied to the coupling capacitor so that an impedance of the synthetic circuit component is increased over a certain range of frequencies selected to reduce the amplitude deterioration.

7. A method for reducing component size in an amplifier circuit comprising:

coupling a coupling capacitor to a synthetic circuit component and an amplifier, wherein the synthetic circuit component comprises a conductor and a resistive element, and the conductor and the resistive element are coupled together;

coupling a bootstrap amplifier to the coupling capacitor and the synthetic circuit component;

and the bootstrap amplifier providing a drive signal to the synthetic circuit component derived from a signal applied to the coupling capacitor so that an impedance of the synthetic component is increased over a certain range of frequencies selected to reduce the size of the coupling capacitor.

8. A method for reducing a recovery time of an amplifier circuit comprising:

coupling a coupling capacitor to a synthetic circuit component and an amplifier, wherein the synthetic circuit component comprises a conductor and a resistive element, and the conductor and the resistive element are coupled together;

coupling a bootstrap amplifier to the coupling capacitor and the synthetic circuit component;

and the bootstrap amplifier providing a drive signal to the synthetic circuit component derived from a signal applied to the coupling capacitor so that an impedance of the synthetic component is increased over a certain range of frequencies selected to reduce the recovery time of the amplifier circuit.

9. An amplifier circuit comprising:

a synthetic circuit component and an amplifier that receive an input signal; and

a bootstrap amplifier having an output that is coupled to the synthetic circuit component for producing a drive signal provided to the synthetic circuit component, wherein the synthetic circuit component comprises a conductor and a resistive element, the conductor and the resistive element are coupled together, the drive signal being derived from the input signal, and the parasitic capacitance of the synthetic circuit component is operable to be controlled by applying the drive signal to the conductor.

11. The amplifier circuit of claim 9 further comprising a coupling capacitor, the coupling capacitor being interposed between the synthetic circuit component and the input signal.

10. An amplifier circuit comprising:

a synthetic circuit element and an amplifier that receives an input signal; and

a bootstrap amplifier coupled to the synthetic circuit element for producing a drive signal provided to the synthetic circuit component, the drive signal being derived from the input signal and applied to the synthetic circuit component to compensate for at least some of the parasitic capacitance associated with synthetic element, wherein the bootstrap amplifier is a variable gain amplifier.