Browse Prior Art Database

Active Circuit to Cancel Power Supply Electrical Noise

IP.com Disclosure Number: IPCOM000040112D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Bustamante, CM: AUTHOR [+2]

Abstract

A technique is described whereby an electrical circuit converts an electrically noisy power supply line to a quiet linear power supply line. The concept is designed to provide integrated power circuitry that is free of noise spikes and glitches, which have detrimental effects on the operation of sensitive analog sensing circuitry. Sensitive analog circuits, such as fiber-optic receivers, diffuse infrared receivers, analog-to-digital converters and calibrated instrumentation, which use sensing equipment to measure currents as low as 25 nA, are subject to the detrimental effects of power supply electrical noise. Three circuit techniques are described which effectively cancel out line noise and glitches which cause the detrimental operation of the analog equipment.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Active Circuit to Cancel Power Supply Electrical Noise

A technique is described whereby an electrical circuit converts an electrically noisy power supply line to a quiet linear power supply line. The concept is designed to provide integrated power circuitry that is free of noise spikes and glitches, which have detrimental effects on the operation of sensitive analog sensing circuitry. Sensitive analog circuits, such as fiber-optic receivers, diffuse infrared receivers, analog-to-digital converters and calibrated instrumentation, which use sensing equipment to measure currents as low as 25 nA, are subject to the detrimental effects of power supply electrical noise. Three circuit techniques are described which effectively cancel out line noise and glitches which cause the detrimental operation of the analog equipment. The overall concept uses the virtual grounding effect of an op-amp for the purpose of actively cancelling out power line noise. It also adds AC regulation to an already DC regulated line, thereby eliminating the need of implementing a separate DC regulator. The grounding concept, as shown in Fig. 1, provides an internal voltage loop 10, so as to enable node 11 to be virtually at ground level, free of noise in the frequency range of from O Hz to the upper frequency of operational amplifier (op-amp) 12. Node 13 will be at virtual ground from a frequency range of 3 Hz to 440 MHz. (Note - Node 13 can have any DC voltage and still be a quiet AC ground.) Expanding on the grounding concept, the circuit in Fig. 2 shows the full integrated circuitry. The noise on the power +12v line is generally caused by digital switching, usually fr...