Abstract:
A circuit for providing regulated power to a microelectronic device is disclosed. The circuit includes an error amplifier, a transistor, and a supplemental voltage supply coupled to the transistor. The supplemental voltage supply supplies requisite bias to operate the transistor near its saturation point.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application Serial No. 60/178,357, filed Jan. 27, 2000, entitled “Microelectronic Current Regulator.” 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to microelectronic integrated circuits. More particularly, the present invention relates to microelectronic power regulation circuits. 
     BACKGROUND OF THE INVENTION 
     Regulators are often employed to provide a desired, regulated power to microelectronic devices such as microprocessors. For example, switching regulators such as buck regulators are often used to step down a voltage (e.g., from about 3.3 volts) and provide suitable power to a microprocessor (e.g., about 10-30 amps at about 2-3 volts). 
     To increase speed and reduce costs associated with microprocessors, microprocessor gate counts and integration generally increase, while the size of the microprocessor per gate generally decreases. As gate counts, speed, and integration of microprocessors increase, supplying requisite power to microprocessors becomes increasingly problematic. For example, a current required to drive the processors generally increases as the number of processor gates increases. Moreover, as the gate count increases per surface area of a processor, the operating voltage of the processor must typically decrease to, among other reasons, reduce overall power consumption of the processor. 
     As microprocessor power demands increase, use of typical power regulators to control and supply requisite power becomes increasingly problematic. For example, the regulator may consume a relatively large amount of power during operation. This power consumption may be problematic in several regards. For example, such power consumption reduces an amount of power transmitted through the regulator to the microprocessor. Further, any heat generated by the regulator&#39;s consumption of power must be dissipated and subtracts from a thermal budget allotted to the microprocessor. Accordingly, improved power regulators suitable for regulating high current, which dissipate relatively little power are desired. 
     SUMMARY OF THE INVENTION 
     The present invention provides improved apparatus and techniques for regulating power to a microelectronic device. More particularly, the invention provides improved devices and methods suitable for supplying electronic devices with relatively high, regulated current, with relatively little power loss. 
     The way in which the present invention addresses the deficiencies of now-known regulators and power supply systems is discussed in greater detail below. However, in general, the present invention provides an additional voltage source to operate a pass transistor of a linear regulator close to its saturation point. This allows the regulator to run more efficiently and thus consume less power during operation. 
     In accordance with one exemplary embodiment of the present invention, a regulator includes an error amplifier, a transistor, a compensation network, a reference voltage source, a supplemental voltage source, an input voltage terminal, an output voltage terminal, and a Schottky clamp. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The drawing FIGURE illustrates a power regulation system in accordance with an exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The present invention generally relates to microelectronic power regulators. More particularly, the invention relates to regulators suitable for providing high current, high speed power to microelectronic devices and to electronic systems including the regulators. Although the present invention may be used to provide power to a variety of microelectronic devices, the invention is conveniently described below in connection with providing power to microprocessors. 
     The drawing FIGURE schematically illustrates a power regulation circuit  100  in accordance with an exemplary embodiment of the present invention. Exemplary circuit  100  includes an error amplifier  110 , a transistor  120 , a compensation network  130  coupled to an emitter region of the transistor, a Schottky clamp  140 , a reference voltage source  150 , a supplemental voltage source  160 , an input voltage terminal  170 , and an output voltage terminal  180 . 
     In general, circuit  100  is configured to provide high current output (e.g., 100 amps or more), while consuming relatively little power. More particularly, circuit  100  is designed such that transistor  120  operates near its saturation point to reduce resistance through transistor  120  and consequently reduce a base-emitter voltage drop (V BE ) across the transistor. 
     In operation a relatively high voltage (e.g., from supplemental voltage source  160 ) is applied to an input or base region of transistor  120  to cause transistor  120  to operate near its saturation point. In accordance with one embodiment of the invention, the relatively high voltage is applied to amplifier  110 . Supplemental voltage source  160  is suitably configured to supply transistor  120  with any voltage greater than voltage applied at input source  170 . For example, source  160  may supply error amp  110  with a voltage of 3.3 volts, where input  170  voltage is about 1.1 volt and voltage at output  180  is about 1.0 volt. 
     Schottky clamp  140  is suitably configured to prevent forward biasing of transistor  120 . Thus, a voltage higher than voltage at input  170  may be applied to a base region of transistor  120  without forward biasing transistor  120 . Clamp  140  is suitably coupled to a base region of transistor  120 , input voltage  170 , and a collector region of transistor  120 . 
     Transistor  120  is preferably an N-P-N transistor. In addition, transistor  120  is preferably formed on a semiconductive substrate having relatively high conductor mobility—for example, a compound semiconductor material such as silicon germanium, gallium arsenide, or the like. 
     Although the present invention is set forth herein in the context of the appended drawing figure, it should be appreciated that the invention is not limited to the specific form shown. For example, while the invention is conveniently described above in connection with an N-P-N transistor, other forms of transistors may suitably be used in connection with the present invention. Various other modifications, variations, and enhancements in the design and arrangement of the method and apparatus set forth herein may be made without departing from the spirit and scope of the present invention as set forth in the appended claims.