Amplifiers – With semiconductor amplifying device – Including plural amplifier channels
Reexamination Certificate
2000-03-29
2001-10-30
Mottola, Steven J. (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including plural amplifier channels
C330S253000
Reexamination Certificate
active
06310520
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to operational amplifiers and more particularly to a high precision operational amplifier which is intermittently operational and providing a low quiescent power requirement when in a standby state while providing a high slew rate when activated.
2. Description of Related Art
One of the challenges for wireless communications apparatus currently being developed and implemented with integrated circuits is to keep both active and standby power consumption low. For standby operation, circuits are turned on very briefly and then powered down as quickly as possible to minimize power consumption. However, for high precision analog circuit modules, such as analog to digital and digital to analog converters, reference voltage sources are often required for which large filter capacitors are employed to maintain low noise levels. In such instances, there are typically two choices for intermittent operation: (1) maintain buffering of the capacitor voltage between activity bursts; or (2) utilize a high slew rate to quickly recharge the capacitor at the beginning of each activity burst. The first option requires that reference and buffer circuits remain powered up continuously between bursts, while the second option requires that it must be possible to recharge the capacitor, typically in the range of 1 nF to 1 uF, quickly at the beginning of each activity burst. For some systems, the rapid recharge of the capacitor can require peak currents of 100 to 1000 times what is necessary to maintain the charge in normal operation. In both instances, power dissipation presents a formidable problem and in some instances can be excessive.
SUMMARY
Accordingly, it is an object of the present invention to provide an improvement in operational amplifiers where it is necessary to keep both active and standby power consumption at a relatively low level.
It is another object of the invention to provide an improvement in high precision analog circuit modules comprised of operational amplifiers.
It is still another object of the invention to provide an improvement in operational amplifiers implemented with semiconductor devices including MOS transistors CMOS transistors, and bipolar transistors.
It is still yet another object of the invention to provide a high precision analog circuit module including one or more voltage reference sources including relatively large capacitors which must maintain a reference voltage continuously or quickly recharged at the beginning of an operational mode.
Briefly, the foregoing and other objects are achieved by combining a conventional operational amplifier with a secondary high power operational amplifier that is activated only during brief periods for which a very high slew rate is required to charge a load capacitor which operates as a voltage reference source. This is achieved by an amplifier architecture which is comprised of a capacitor load circuit for providing an output voltage of a predetermined amplitude; a first operational amplifier circuit, operable as a main amplifier, connected to the load circuit for powering the load circuit under normal operating condition; and a second operational amplifier circuit, operable as an auxiliary amplifier, connected to the load circuit for additionally powering the load circuit together with the main amplifier during relatively short intervals and where a relatively high slew rate is required for the output voltage. The amplifier architecture is preferably implemented in one or more integrated circuits.
Further scope of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood, however, that the detailed description and specific examples, while disclosing the preferred embodiments of the invention, they are provided by way of illustration only, since various changes and modifications coming within the spirit and scope of the invention will become apparent to those skilled in the art from the following detailed description.
REFERENCES:
patent: 5880627 (1999-03-01), Thiel
Agere Systems Guardian Corp.
Mottola Steven J.
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