Ex parte Ferrario

Board of Patent Appeals and Interferences

Sep 24, 1999

08098740 (B.P.A.I. Sep. 24, 1999)

Application for patent filed July 28, 1993.1
THIS OPINION WAS NOT WRITTEN FOR PUBLICATION
The opinion in support of the decision entered today (1) was not written for publication
in a law journal and (2) is not binding precedent of the Board.
Paper No. 29
UNITED STATES PATENT AND TRADEMARK OFFICE
__________________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
__________________
Ex parte BRUNO FERRARIO
__________________
Appeal No. 96-2614
Application 08/098,7401
________________
ON BRIEF
________________
Before HAIRSTON, LEE and RUGGIERO, Administrative Patent
Judges.
LEE, Administrative Patent Judge.
DECISION ON APPEAL
This is a decision on appeal under 35 U.S.C. § 134 from
the examiner’s rejection of claims 1-22. No claim has been
allowed.
References relied on by the Examiner
Pirez et al. (Pirez) 5,034,626 July 23,
1991
Carroll 5,130,571 July 14,
1992
Appeal No. 96-2614
Application 08/098,740
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The applicant’s admitted prior art as depicted in Figure 1 of
the
specification.
The Rejections on Appeal
Claims 5 and 9 stand rejected under 35 U.S.C. § 103 as
being unpatentable over the appellant’s admitted prior art as
depicted in Figure 1 of the specification, in view of Carroll.
Claims 1-3, 4, 6, 7, 8, 10, 11, 12-20, 21 and 22 stand
rejected under 35 U.S.C. § 103 as being unpatentable over the
appellant’s admitted prior art as depicted in Figure 1 of the
specification, in view of Carroll and Pirez.
The Invention
The invention is directed to a capacitance multiplier
circuit (claims 1, 5 and 9), a method for providing a large RC
time constant (claim 13), and a method for temperature
compensating an RC circuit including a capacitor multiplier
circuit (claim 17). Claims 1, 5, 9, 13 and 17 are the only
independent claims. Claims 5 and 17 are representative and
are reproduced below:
Appeal No. 96-2614
Application 08/098,740
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5. An integrated capacitance multiplier circuit
comprising:
a capacitor having a first terminal connected
to a lower common voltage, and also having a second
terminal;
an operational amplifier having an output
connected to an inverting input thereof, and having
a non-inverting input connected to said second
terminal of said capacitor;
a biasing circuit with at least two separate
bias voltage outputs;
first and second field effect transistors having
respective source regions thereof electrically
connected together, and having respective gates
connected to said bias voltage outputs of said
biasing circuit;
said first transistor having a drain region
connected to said second terminal of said capacitor,
and
said second transistor having a drain region
connected to said output of said operational
amplifier; and
a multiplied-capacitance connection at said
sources of said transistors; whereby said
multiplied-capacitance connection provides an
effective capacitance to said common voltage which
is a multiple of the physical capacitance of said
capacitor, multiplied in an amount which depends on
the ratio of the conductances of said transistors.
17. A method for temperature compensating an
integrated RC circuit which comprises an integrated
resistor, an integrated capacitor and an integrated
capacitance multiplier circuit capable of virtually
multiplying the capacitance of said integrated
Appeal No. 96-2614
Application 08/098,740
4
capacitor by a term given by the ratio between two
resistances to give a virtual capacitance value,
comprising:
(a) utilizing as said two resistances the ON
resistances of two field effect transistors of
different size;
(b) biasing at least one of said transistors with a
temperature dependent voltage for modifying the
relative ON-resistance of the transistor and said
ratio between ON resistances in function of
temperature, thus varying said virtual capacitance
value of the RC circuit in function of temperature
to compensate a variation of the value of the
integrated resistor of the RC circuit.
Opinion
The rejection of claims 1-22 cannot be sustained.
A reversal of the rejection on appeal should not be
construed as an affirmative indication that the appellants’
claims are patentable over prior art. We address only the
positions and rationale as set forth by the examiner and on
which the examiner’s rejection of the claims on appeal is
based.
In claims 1, 5 and 9, what is claimed is a capacitance
multiplier circuit. In claim 13, what is claimed is a method
for providing a large RC time constant. In claim 17, what is
claimed is a method for temperature compensating an integrated
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Application 08/098,740
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RC circuit. But in all of the appellant’s claims, it is
required that the resistance or conductance provided by two
field effect transistors be used to enhance or multiply the
capacitance otherwise provided by a capacitor. That is the
key idea.
Capacitor multiplier circuits have been known. The
appellant’s Figure 1 illustrates the acknowledged prior art
circuits of this kind. As is evident in a comparison of
Figure 1 with appellant’s claims, see for example claim 5, the
prior art circuit makes use of two resistors R1 and R2,
whereas the appellant’s claims recite not first and second
resistors but two field effect transistors with suitable
biasing.
At page 4 of the answer, the examiner stated: “Note that
although reference Carroll is used in this rejection to show
that a transistor can be used as a resistor, the fact that a
transistor can be used as a resistor is notoriously well known
in the art . . . .” According to the examiner, “it is
fundamentally basic and notoriously well known in the art that
a transistor can function as a variable resistor by varying
the biasing voltage, and that a transistor can function as a
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Application 08/098,740
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constant resistor by biasing the transistor with a constant
biasing voltage” (Examiner’s Answer at page 10). The only
evidence the examiner cited in support of the finding
concerning using transistors as resistors is Carroll. The
examiner stated (Answer at pages 8-9) that “Carroll teaches
transistors can be used as resistors,” that “[Carroll’s]
transistor operates as a switch but also as a resistor when it
is turned on,” and that “the resistance across the channel of
the [Carroll] transistors is desirable and intentional.”
We agree with the appellant that the examiner’s reading
of Carroll is misplaced and erroneous. The fact that
transistors have intrinsic resistance/conductance does not
translate or equate to a general teaching for using
transistors as resistors. That such intrinsic resistance can
be selected to vary the operating characteristics of a
transistor in one way or another as a switch, either for
changing the acquisition time or for affecting charge
injection, is not a suggestion for using the transistor as a
resistor. We have read the portions of Carroll cited by the
examiner, i.e., column 1, lines 20-48, and column 2, line 67
to column 3, line 67, and do not find therein any teaching or
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Application 08/098,740
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reasonable suggestion for using transistors as resistors. The
transistors disclosed in Carroll are used only for switching
purposes. While Carroll does discuss the equivalent
resistance of a field effect transistor, it is only in the
context of how it affects the charge time of a switched
capacitor and switch induced charge injection. The examiner
has not pointed to any portion of Carroll which reasonably
would have suggested using a biased transistor not for its
switching capabilities but as a resistor.
The examiner’s important finding that it was notoriously
well known in the art to use biased transistors as resistors
is not supported by adequate factual evidence. Accordingly,
the rejection of claims 5 and 9 over the admitted prior art
and Carroll cannot be sustained.
The rejection of claims 1-4, 6-8, and 10-22 over the
admitted prior art, Carroll, and Pirez also cannot be
sustained because as applied by the examiner Pirez does not
make up for the
above-discussed deficiencies of the admitted prior art and
Carroll. The examiner has not articulated how Pirez would
Appeal No. 96-2614
Application 08/098,740
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have reasonably suggested using biased transistors as
resistors.
While not necessary, we include the following discussion
to indicate several points with which we disagree with the
appellant. It may be useful if and when the examiner has
found sufficient factual basis to support his finding that it
was notoriously well known to use transistors as resistors.
First, a transistor can be fixedly biased and thus a “biasing
circuit” as recited in claim 1 can well be a power supply.
Secondly, assuming that it would have been obvious to one with
ordinary skill in the art to use a transistor as a resistor,
it follows that any one or more resistor in a circuit may be
implemented by a transistor, at the discretion of one with
ordinary skill in the art. There is no reason to limit that
discretion to an all or nothing choice. The motivation is
simply the recognition that a
resistor may be implemented by a properly biased transistor
and need not have anything to do with the appellant’s focus on
capacitance multiplier circuits.
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Application 08/098,740
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We do not express a view one way or another with respect
to the arguments of the appellant as directed to certain
dependent claims, which we have not specifically addressed
above.
Conclusion
The rejection of claims 5 and 9 under 35 U.S.C. § 103 as
being unpatentable over the appellant’s admitted prior art as
depicted in Figure 1 of the specification, in view of Carroll.
is reversed.
The rejection of claims 1-3, 4, 6, 7, 8, 10, 11, 12-20,
21 and 22 under 35 U.S.C. § 103 as being unpatentable over the
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Application 08/098,740
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appellant’s admitted prior art as depicted in Figure 1 of the
specification, in view of Carroll and Pirez is reversed.
REVERSED
KENNETH W. HAIRSTON )
Administrative Patent Judge )
)
)
)
)
) BOARD OF PATENT
JAMESON LEE ) APPEALS AND
Administrative Patent Judge ) INTERFERENCES
)
)
)
)
)
JOSEPH RUGGIERO )
Administrative Patent Judge )
Christopher F. Regan
ALLEN, DYER, DUPPELT,
Appeal No. 96-2614
Application 08/098,740
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MILBRATH & GILCHRIST, P.A.
P. O. Box 3791
Orlando, FL 32802-3791
Appeal No. 96-2614
Application 08/098,740
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Yolunda/Sonja: Please put attorney’s name and address here.
Thanks.