Amplifiers – With periodic switching input-output
Reexamination Certificate
2001-12-10
2003-02-04
Tokar, Michael (Department: 2819)
Amplifiers
With periodic switching input-output
C330S253000, C330S109000, C330S107000, C330S267000, C330S261000, C330S254000, C330S297000, C327S124000, C341S118000, C341S120000, C341S143000
Reexamination Certificate
active
06515540
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to conditionally stable operational amplifiers.
SUMMARY
An operational amplifier is a relatively high gain amplifier capable of being used in various kinds of feedback circuits. An operational amplifier circuits can, for example, provide programmable gain, signal summation, integration, and differentiation, and various other useful functions.
The most popular variety of operational amplifier has high-impedance differential signal inputs and a low impedance signal output, and functions as a high-gain differential voltage amplifier. Another kind of operational amplifier, known as an “operational transconductance amplifier,” has high-impedance differential signal inputs and a high-impedance signal output, and functions as a differential voltage to current converter.
High accuracy operational amplifier circuits require large gain from zero frequency up to a certain closed-loop bandwidth. Most general-purpose operational amplifiers are constructed with a dominant pole in the open-loop frequency response in order to guarantee stability when any purely resistive voltage divider network provides a feedback signal. When the operational amplifier has such an open-loop frequency response, an enormous gain-bandwidth product is required for high accuracy. Designers of low-power or high-accuracy operational amplifier circuits have therefore considered conditional stability as a way of avoiding the gain-bandwidth product limitation of unconditionally stable operational amplifiers. A conditionally-stable operational amplifier has at least 180 degrees of phase lag for a frequency less than the frequency at which the operational amplifier has an open-loop unity gain, but the phase lag decreases to less than 180 degrees as the frequency increases to the open-loop unity gain frequency.
In accordance with a described embodiment, stability of a conditionally stable operational amplifier is ensured against large signals and transients (and associated saturation of the amplifier circuit) by use of a saturation detector and bypass circuits which collapses the system to an unconditionally stable system. The conditionally stable operational amplifier includes at least three integrator stages in a low frequency path from a signal input to a signal output, and a bypass path for bypassing at least one of the integrator stages in the maximum integration path. The bypass path(s) and the maximum integration path converge at a summing node combining signal from the low-frequency path with signal from the bypass path(s). According to this embodiment, stability of a conditionally stable multi-path operational amplifier is ensured against large signals and transients by disabling or bypassing low-bandwidth integrators when the output of the amplifier system is saturated.
REFERENCES:
patent: 3989961 (1976-11-01), Masreliez
patent: 3991730 (1976-11-01), Crall
patent: 4318613 (1982-03-01), Waiwood
patent: 4384257 (1983-05-01), Nola
patent: 4429281 (1984-01-01), Ito et al.
patent: 4502020 (1985-02-01), Nelson et al.
patent: 4509037 (1985-04-01), Harris
patent: 4559502 (1985-12-01), Huijsing
patent: 4559634 (1985-12-01), Hochschild
patent: 4628279 (1986-12-01), Nelson
patent: 4713628 (1987-12-01), Nelson
patent: 4757270 (1988-07-01), Rokos
patent: 4757275 (1988-07-01), Saller et al.
patent: 4766367 (1988-08-01), Saller et al.
patent: 4780689 (1988-10-01), Saller et al.
patent: 4808942 (1989-02-01), Milkovic
patent: 4906944 (1990-03-01), Frerking
patent: 4924189 (1990-05-01), Senn et al.
patent: 4926178 (1990-05-01), Mallinson
patent: 4939516 (1990-07-01), Early
patent: 4994805 (1991-02-01), Dedic et al.
patent: 5012244 (1991-04-01), Wellard et al.
patent: 5298813 (1994-03-01), Tanigawa et al.
patent: 5317277 (1994-05-01), Cavigelli
patent: 5446405 (1995-08-01), Ikeda
patent: 5451901 (1995-09-01), Welland
patent: 5477481 (1995-12-01), Kerth
patent: 5499027 (1996-03-01), Karanicolas et al.
patent: 5635871 (1997-06-01), Cavigelli
patent: 5757301 (1998-05-01), Kuo et al.
patent: 5798664 (1998-08-01), Nagahori et al.
patent: 6002299 (1999-12-01), Thomsen
patent: 6037891 (2000-03-01), Griph
patent: 6111606 (2000-08-01), Ikeda
Pernici et al., A CMOS Low-Distortion Fully Differential Power Amplifier with Double Nested Miller Compensator, IEEE Journal of Solid-State Circuits, vol. 28, No. 7, pp. 758-763 (Jul. 1993).
Eschauzier, et al., Frequency Compensation Techniques for Low-Power Operational Amplifiers, Kluwer Academic Publishers, pp. 166-173 (1995).
Eschauzier, et al., A 100 MhZ 100-dBOperational Amplifier with Multipath Nested Miller Compensation Structure, IEEE Journal of Solid-State Circuits, vol. 27, No. 12, pp. 1709-1716 (Dec. 1992).
Yu et al., A high-Swing 2-V CMOS Operational Amplifier with Replica-Amp Gain Enhancement, IEEE Journal of Solid-State Circuits, vol. 28, No. 12, pp. 1265-1271 (Dec. 1993).
OP'T CYNDE et al., A CMOS Large-Swing Low Distortion Three-Stage Class AB Power Amplifier, IEEE Journal of Solid-State Circuits, vol. 25, No. 1, pp. 265-273 (Feb. 1990).
Lee, Wai Laing, A Novel Higher Order Interpolative Modulator Topology for Higher Resolution Oversampling and Converters, Master's Thesis, Massachusetts Institute of Technology, pp. 1-135 (Jun. 1987).
Lee et al., A Topology for Higher Order Interpolative Coders, IEEE, pp. 459-462 (1987).
Gardner, Floyd M., Phaselock Techniques, 2nd Edition, Wiley-Interscience, pp. 16-25, (1979).
Schwarz et al., Linear Systems, McGraw-Hill Book Co., pp. 422-429 (1965).
Grebene, Alan B., Analog Integrated Circuit Design, Van Nostrand Reinhold Company, pp. 155-170 (1972).
Hsieh et al., A low-Noise Chopper-Stabilized Differential Switched-Capacitor Filtering Technique, IEEE Journal of Solid-State Circuits, vol. SC-16, No. 6, pp. 708-715 (Dec. 1981).
Mehr et al., Discrete-Time Feedback Structures for High Precision Analog Signal Processing, IEEE Transactions on Circuits and Systems-II: Analog and Digital Signal Processing, vol. 43, No. 1, pp. 60-62 (Jan. 1996).
Enz et al., Circuit Techniques for Reducing the Effects of Op-Amp Imperfections: Autozeroing Correlated Double-Sampling and Chopper Stabilization, Proceedings of the IEEE, vol. 84, No. 11, pp. 1584-1614 (Nov. 1996).
Norsworth et al., Delta-Sigma Data Converters Theory, Design and Stimulation, IEEE Press, pp. 183-185 (1997).
Franco, Sergio, Design with Operational Amplifiers and Analog Integrated Circuits, McGraw-Hill Book Company, pp. 264-291 (1988).
You et al., A Multistage Amplifier Topology with Nested Gm-C Compensation for Low-Voltage Application, ISSCC, pp. 2-3 (Feb. 8, 1997).
National Semiconductor, Topics on Using the LM6181-A New Current Feedback Amplifier, National Semiconductor, Application Note 813, pp. 1-10 (Mar. 1992).
Kejariwal Murari
Prasad Ammisetti V.
Thomsen Axel
Cirrus Logic Inc.
Murphy, Esq. James J.
Nguyen Linh Van
Tokar Michael
Winstead Sechrest & Minick P.C.
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