Amplifiers – With semiconductor amplifying device – Including particular power supply circuitry
Reexamination Certificate
2001-11-07
2003-09-16
Tokar, Michael (Department: 2819)
Amplifiers
With semiconductor amplifying device
Including particular power supply circuitry
C330S149000, C323S314000, C326S115000
Reexamination Certificate
active
06621349
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electronic circuits connected to power supplies which produce noisy outputs and more particularly to circuits for reducing the noise introduced by the power supply.
2. Description of Related Art
To some degree, almost all electronic circuits are susceptible to noise on their power supply or ground input lines.
FIG. 1
shows a typical prior art system
10
including a supply voltage VDD input connected through a terminal via line
60
and line
63
to the power supply input of a typical VDD Noise Sensitive Circuit (NSC)
11
. The NSC
11
is also connected by lines
66
and
64
to ground (reference potential) connection of the VDD power supply to complete to the power supply circuit connection as will be well understood by those skilled in the art. Unfortunately, the power supply voltage includes a noise signal NS which is an unwanted component included with the direct current voltage VDD. A control circuit
12
is also included in system
10
. The control circuit
12
is connected to receive power from the power supply through the lines
62
and
60
. The ground of the control circuit
62
is connected by lines
65
and
64
to ground (reference potential) to complete the connections to the power supply. The control circuit provides control signals on output line
52
connected to an input of the NSC
11
.
The typical VDD noise sensitive circuit
11
is sensitive to an unwanted input noise signal NS which is representative of certain frequencies included with the Direct Current (DC) power supply voltage VDD on line
60
which cause an unacceptable operational problem for the NSC
11
. For example, in
FIG. 1
, the output signal OS is shown on the output line
9
from NSC
11
. Thus the output signal OS from the NSC
11
is noisy and in many applications, the noise must be substantially reduced in amplitude for the output signal OS to meet specifications.
In summary the noise NS received by control circuit
12
and noise sensitive circuit
11
has an unwanted harmful effect on the typical noise sensitive circuit
11
producing an output noise signal OS along with the output signal from circuit
11
on line
9
.
FIG. 2
is a modification of the electrical schematic diagram of
FIG. 1
which shows a prior art method for combating the noise sensitivity problem by adding a decoupling capacitor
15
across to the power supply to reduce the noise output signal OS′ on output line
9
. The capacitor
15
can filter out the noise by providing an effective short circuit for the Alternating Current (AC) component of the noise. The upper plate of the capacitor
15
is connected by line
61
to line
60
to the power supply. The lower plate of capacitor
15
is connected by line
67
via to line
64
to ground completing the power supply capacitor circuit. However, when the circuit of
FIG. 2
is embodied on a small microchip the decoupling capacitor
15
can consume too much area on the surface of the small microchip.
FIG. 3
is a modification of the electrical schematic diagram of
FIG. 2
which shows a prior art method in which there are dual output lines
52
′/
52
″ in place of the single output line
52
in FIG.
2
.
Other prior art approaches to combating the noise sensitivity problem require signal processing or filtering of the output of the affected circuit, which can be very complicated and costly.
U.S. Pat. No. 4,630,104 of Nakagaki et al for “Circuit Arrangement for Removing Noise of a Color Video Signal” describes apparatus for color video signal processing to separate noise in a color video signal from the output, then subtract it from the color video signal output. This reference is not directed to solving the problem of power supply noise. A luminance signal and a chroma signal of a color video signal are processed to generate a first signal and a second signal, respectively. The first signal indicates the contour line of images represented by the video signal. The second signal includes noise included in the chroma signal and a signal component having an amplitude substantially equal to the peak to peak value of the noise. The first and second signals are fed to either a switching circuit or a multiplier so that a resultant output signal having only the noise is obtained. The noise components are then subtracted, by way of a subtractor, from the chroma signal so that a chroma signal having no noise will be obtained.
U.S. Pat. No. 4,475,215 of Gutleber entitled “Pulse Interference Cancelling System for Spread Spectrum Signals Utilizing Active Coherent Detection” describes a pulse interference canceling system for spread spectrum signals utilized in a digital noise coded communications system. A noise coded signal that is phase shifted by 180° is added to the original to cancel noise and to recover the coded signal. The system includes first and second noise coded signal channels located in a noise coded signal receiver which also includes a demultiplexer for providing a pair of received noise coded signals which were initially generated, multiplexed and transmitted to the receiver. First and second coherent detectors are coupled to both signal channels, the first being directly coupled thereto so that no signal delay exists. The second is coupled to the two signal channels with respective first and second variable time delay circuits having a delay substantially equal to the bit width of each digital code as well as a vernier delay which is adapted to delay the phase of any received pulse interference in the respective channel so that it is exactly 180° out of phase with the same undelayed pulse interference. Signal summing means are coupled to the outputs of the two coherent detectors which operate to completely cancel the interference pulse signal while leaving the desired noise coded signal at its peak amplitude.
U.S. Pat. No. 6,052,420 of Yeap et al. entitled “Adaptive Multiple Sub-band Common-mode RFI Suppression” uses a common mode signal to estimate noise in narrow frequency band. The estimate is subtracted from the original signal. A noise suppression circuit for a two wire communications channel comprising a hybrid device, e.g. a hybrid transformer or circuit, which provides a differential mode signal corresponding to a differential signal received from the channel. A summing device extracts from the channel wires a common mode signal that it supplies to a noise estimation unit that derives a common mode signal as an estimate of a noise level in a frequency band having a bandwidth narrower than an operating channel bandwidth. The noise estimation unit adjusts the amplitude of the noise estimate to correspond to the residual noise in the differential mode signal and subtracts it from the differential mode signal to produce a noise-suppressed output signal. A noise detection and control unit scans the operating band, identifies a frequency band having a highest noise level, and sets the noise estimation unit to the detected noisy band. The noise estimation unit suppresses the noise in that band. Preferably, the noise estimation unit comprises several channels, with a tunable filter, a phase shifter and an amplifier, and the noise detection and control unit sets the channels, in succession, to different frequency bands in descending order of noise level. The noise detection and control unit may cross-correlate the common mode signal and the noise-suppressed output signal and adjust the amplification of the noise estimation signal to reduce residual differential mode noise towards zero.
U.S. Pat. No. 6,061,456 of Andrea entitled “Noise Cancellation Apparatus” discloses a transducer for an acoustic noise cancellation apparatus for reducing background noise using microphones and amplifiers. The transducer includes a housing with first microphone for receiving a first acoustic sound, composed mainly of speech and background noise, that converts the first acoustic sound to a first signal. A second microphone is arranged at an angle, close to the first microphone to receive a
Jones II Graham S.
Nguyen Linh V
Schnurmann H. Daniel
Tokar Michael
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