Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Nonlinear amplifying circuit
Reexamination Certificate
2003-01-27
2004-05-11
Le, Dinh T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
Nonlinear amplifying circuit
C330S258000
Reexamination Certificate
active
06734721
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to electrical circuits known as closed-loop circuits. By way of example and not by way of limitation, a common-mode feedback loop is described herein as an exemplary embodiment of such a closed-loop circuit. One skilled in the art will easily recognize that the method and apparatus of the present invention may be advantageously employed with other closed-loop circuits.
A critical design consideration of closed-loop circuits is to ensure that the circuits are stable. A common criterion of stability is to design a loop so that its open loop phase margin is sufficiently large. A typical such design consideration is to ensure that open loop phase margin is >45°. It is particularly desirable to have open loop phase margin be in the range of 60°-90°.
Phase margin (&PHgr;
M
) is inversely proportional to loop bandwidth (LBW). Settling time T
S
of a loop circuit is also inversely proportional to LBW. Thus, there is a trade off between &PHgr;
M
and T
S
. A smaller LBW gives a higher &PHgr;
M
at the expense of a longer T
S
. A larger LBW may also be established with a shorter T
S
, but with a lesser &PHgr;
M
.
There is a need for a method and apparatus for affecting speed of transition of a closed loop circuit from an initial state to a steady state that improves settling time T
S
while maintaining phase margin &PHgr;
M
at an acceptable value.
SUMMARY OF THE INVENTION
A method for affecting speed of transition of a closed loop circuit from an initial state to a steady state during a transition period; the closed loop circuit including a switching unit effecting the transition in response to a gating signal applied to a gate locus at a value greater than a predetermined threshold potential; includes the steps of: (a) at least one of: (1) clamping the gate locus at a minimum potential greater than ground potential and less than the predetermined threshold potential; and (2) increasing potential at the gate locus at a plurality of various rates during a plurality of segments of the transition period.
An apparatus for affecting speed of transition of a closed loop circuit from an initial state to a steady state during a transition period; the closed loop circuit including a switching unit effecting the transition in response to a gating signal applied to a gate locus at a value greater than a predetermined threshold potential; comprises: (a) at least one of: (1) a clamping means coupled with the gate locus for clamping the gate locus at a minimum potential greater than ground potential and less than the predetermined threshold potential; and (2) a potential controlling means coupled with the gate locus for increasing potential at the gate locus at a plurality of various rates during a plurality of segments of the transition period.
It is, therefore, an object of the present invention to provide a method and apparatus for affecting speed of transition of a closed loop circuit from an initial state to a steady state that improves settling time T
S
while maintaining phase margin &PHgr;
M
at an acceptable value.
REFERENCES:
patent: 5381114 (1995-01-01), Pena-Finol et al.
patent: 5986502 (1999-11-01), Nakamura
patent: 6043702 (2000-03-01), Singh
Brady W. James
Le Dinh T.
Swayze, Jr. W. Daniel
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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