Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2000-09-01
2002-04-09
Vu, Bao Q. (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S284000, C323S274000
Reexamination Certificate
active
06369554
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear regulator to provide a regulated voltage to a load and particularly relates to frequency compensation for such a linear regulator.
2. Background of the Invention
Linear regulators are well-known devices that provide a regulated voltage to a load based on a source voltage and (usually) a reference voltage.
FIG. 1
shows a conventional arrangement in which linear regulator
10
is connected to a source voltage V+ and provided with a reference voltage Vref so as to provide a regulated voltage to load
12
.
To compensate for frequency-induced variations in current drawn by load
12
, a load capacitor C
L
is often provided. Because there are often high fluctuations in the current drawn by load
12
, however, a large value for C
L
is required, typically from 1 to 100 &mgr;f. Such a large value is disadvantageous since large capacitors are large physically and also expensive.
As seen in
FIG. 2
, a conventional linear regulator
10
includes a bipolar device BP
2
connected between the source voltage and the load so as to provide a regulated output voltage. The regulated output voltage is stabilized with a unity gain negative feedback amplification circuit through amplifier A
1
which is provided with a reference voltage. A capacitive amplification circuit
13
includes a bipolar device BP
1
, amplifier A
3
and capacitor Cm in a feedback relationship.
Although good results have been obtained with the linear regulator shown in
FIG. 2
, difficulties are still encountered. Most notably, the frequency roll off characteristics of the linear regulator shown at
10
are highly dependent on the actual value of the current drawn by load
12
. Thus, for example, highest frequency roll off for linear regulator
10
depends on inherent resistive and capacitive effects of bipolar device BP
2
(shown schematically at r&pgr; and c&pgr;). In addition, the load capacitor C
L
actually includes a small series resistance Rs which introduces at least one additional zero into the frequency response of linear regulator
10
. As a result of the additional zero, as well as the current dependence of system poles, it is easy to introduce instabilities in the linear regulator shown at
10
unless the current range of load
12
is small (for example, between 0 and 200 milliamps) and unless C
L
is a high quality capacitor such that its series resistance Rs is very small.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a linear regulator whose frequency characteristics are less dependent on the amount of current drawn by load
12
, and which exhibits a higher degree of frequency compensation than known linear regulators.
In one aspect, the invention is a linear regulator in which a capacitive amplification circuit includes a MOSFET device connected to the base of a bipolar output device so as to stabilize the current flow from the base to the output. Because a MOSFET device is used rather than the bipolar devices found in the prior art, a linear regulator according to the present invention exhibits frequency characteristics whose dependence is less than that of the prior art.
Thus, a linear regulator operable from a source voltage to provide a regulated voltage to a load includes a bipolar device connected between the source voltage and the load with an output of the bipolar device connected to output the regulated voltage, a feedback amplifier connected in negative feedback relationship between the output of the bipolar device and a reference voltage so as to provide a stabilized voltage, and a capacitor amplification circuit connected between the stabilized voltage and the output of the bipolar device. The capacitive amplification circuit includes a MOSFET device connected to a base of the bipolar device so as to stabilize current flow from the base to the output of the bipolar device. The capacitor amplification circuit includes an amplifier and a capacitor connected in feedback relationship with the output of the linear regulator, with an output of the amplifier stage providing a reference signal to the gate of the MOSFET device. Most preferably, a 1:n current mirror provides even greater current independence for the frequency characteristics of the linear regulator.
This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiment thereof in connection with the attached drawings.
REFERENCES:
patent: 5548205 (1996-08-01), Monticelli
patent: 5648718 (1997-07-01), Edwards
patent: 5852359 (1998-12-01), Callahan, Jr. et al.
patent: 5909109 (1999-06-01), Philips
patent: 5929616 (1999-07-01), Perraud et al.
patent: 6011666 (2000-01-01), Wakamatsu
patent: 6061306 (2000-05-01), Buchheim et al.
patent: 6084387 (2000-07-01), Kancko et al.
patent: 0 985 732 (1999-08-01), None
patent: 0 999 549 549 (1999-11-01), None
patent: PCT/US99/05734 (1999-03-01), None
Paul C. Yu, et al., “A 2.5-V, 12-b, 5-Msample/s Pipeland CMOS ADC,” IEEE Journal of Solid-State Circuits, vol, 31, No. 12, Dec. 1996, pp. 1854-61.
Stephen H. Lewis, et al., “Indirect Testing of Digital-Correction Circuits in Analog-to-Digital Converters with Redundancy,” IEEE Transactions on Circuits and Systems-II: Analog and Digital Signal Processing, vol. 42, No. 7, Jul. 1995, pp. 437-445.
U.S. application No. 09/643, 819, Aram, filed Aug. 22, 2000.
U.S. application No.09/648,770, Aram et al., filed Aug. 28, 2000.
U.S. application No. 09/648,462, Aram et al., filed Aug. 28, 2000.
U.S. application No. 09/648,464, Aram, filed Aug. 28, 2000.
Quantum Online / Inside Hard Disk Drives, “Part 2—A Closer Look at Hard Disk Drives”; “Chapter 3—Inside Hard Disk Drives—How They Work”, Jun. 7, 2000.
Quantum Online/Recent Technological Developments, “Chapter 4-The Impact of Leading—Edge Technology on Mass Storage”, Jun. 7, 2000.
Curtis Settles, “DSP-augmented CPU cores promise performance boost for ultra-compact drives”, Data Storage, May 2000, pp. 35-38.
Stephen H. Lewis, “Optimizing the Stage Resolution in Pipelined, Multistage, Analog-to-Digital Converters for Video-Rate Applications”, IEEE Transactions on Circuits and Systems—II: Analog and Digital Signal Processing, vol. 30, No. 8, Aug. 1992.
Stephen H. Lewis, et al., “A 10-b 20-Msample/s Analog-to-Digital Converter”, IEEE Journal of Solid-State Circuits, vol. 27, No. 3, Mar. 1992, pp. 351-358.
Stephen H. Lewis and Paul R. Gray, “A Pipelined 5-Msample/s 9-bit Analog-to-Digital Converter”, IEEE Journal of Solid-State Circuits, vol. SC-22, No. 6, Dec. 1987, pp. 954-961.
Bhupendra K. Ahuja, “An Improved Frequency Compensation Technique for CMOS Operational Amplifiers”, IEEE Journal of Solid-State Circuits, vol. SC-18, No. 6, Dec. 1983, pp. 629-633.
Sehat Sutardja and Paul R. Gray, “A Pipelined 13-bit, 250-ks/s, 5-V Analog-to-Digital Converter”, IEEE Journal of Solid-State Circuits, vol. 23, No. 6, Dec. 1988, pp. 1316-1323.
Janofsky Eric B.
Marvell International Ltd.
Vu Bao Q.
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