A Low Noise CMOS Voltage Reference

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【文件名】:0743@52RD_A Low Noise CMOS Voltage Reference.pdf
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INTRODUCTION
Although low noise design principles have been used in analog integrated circuits
for many years, relatively little effort has been made to apply these principles to
monolithic CMOS voltage references. Previous analysis has shown that reference noise
is the dominant source of noise in high performance circuits such as A/D and D/A
converters [1]. Methods to reduce error from integrated circuit reference noise may
involve external components such as capacitors or filter networks, or complex circuits to
average the value of the reference voltage over time. These approaches can be greatly
simplified or avoided completely if the voltage reference initially has very low intrinsic
noise. Ideally, the voltage reference circuit should be placed on the same substrate as the
desired CMOS VLSI application. Consequently, there is a need for a high performance
CMOS voltage reference that has much lower output noise that previous circuit
approaches.
This research details the design and performance of a low noise monolithic
CMOS voltage reference using a new topology to minimize intrinsic noise gain in the
circuit while maintaining low temperature coefficients through the application of the
bandgap voltage reference principle [2]. The topology is novel and quite simple, yet the
resulting circuit generates far less output noise than a standard CMOS bandgap reference
while exhibiting a comparably low temperature coefficient. This low noise CMOS
voltage reference is easily trimmed, is relatively insensitive to process variations, and can
operate at supply voltages of 5 V or less. A prototype circuit has been successfully
implemented in a single poly, double metal 1.2 µm n-well process and could also be
constructed in smaller gate length n-well technologies, p-well processes, or BiCMOS
processes.
Before discussing the design and performance of a low noise CMOS voltage
reference, the terms “reference” and “regulator” should be explicitly defined. By
definition, a voltage reference is a circuit that provides a stable output voltage
independent of the supply voltage and temperature [3]. Usually, a voltage reference
lacks the ability to sink or source any appreciable amount of current and may have a high
output impedance. A voltage regulator, on the other hand, can be considered a voltage
reference coupled with an low impedance output stage that allows the circuit to sink
and/or source appreciable current to a load. Since low noise CMOS buffer amplifiers can
be designed using techniques described in this dissertation, no attempt has been made to
extend the results of this voltage reference research to a high output current voltage
regulator, since a low noise voltage regulator is quite easily constructed once a low noise
voltage reference is available.
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[此贴子已经被作者于2007-4-4 15:52:02编辑过]