Design of Low-Voltage Bipolar Operational Amplifiers

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Springer Science & Business Media, Feb 28, 1993 - Technology & Engineering - 193 pages
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Design of Low-Voltage Bipolar Operational Amplifiers discusses the sub-circuits necessary to build a low-voltage operational amplifier. These include rail-to-rail input stages, rail-to-rail output stages, intermediate stages, protection circuitry and frequency compensation techniques. Of each of these, various implementations are examined. Furthermore, the book discusses realizations in silicon of the amplifiers.
The design and implementation of low-voltage bipolar Operational Amplifiers (OpAmps) is fully presented. A low supply voltage is necessary because the tendency towards chip components of smaller dimensions lowers the breakdown voltage of these components. Further, a low supply voltage is favorable because it enables operation of the OpAmp from just one single battery cell. The bipolar technology is chosen, because it is more suited for operation at low-voltages than the MOS technology.
The common-mode input voltage of the OpAmp must be able to have any value that fits within the supply voltage range. Input stages are discussed which are able to realize this at supply voltages down to 1.8 V, as well as down to 1 V.
The output voltage of the OpAmp must be able to have any value within the supply voltage range. One of the 1 V output stages that is discussed, the multi-path driven output stage, also has a high bandwidth with a high gain.
In addition to the input and output stage, the OpAmp comprises an intermediate stage, between the input stage and the output stage, to boost the overall gain of the OpAmp, and a class AB current control.
A frequency compensation technique is used to split apart the pole frequencies in the transfer function. A disadvantage of this nested Miller compensation, is that the resulting bandwidth is reduced by a factor of two. A new method, multi-path-driven Miller compensation, which does not have this drawback, is therefore introduced.
Several realizations are evaluated and a figure of merit is defined for the performance comparison of the OpAmps. One of the OpAmps operates at a 1 V supply, has a 3.4 MHz bandwidth with a 100 pF load and has a 700 &mgr;A supply current.
The book is an excellent reference for professional designers of amplifiers and may be used as a text for advanced courses on the subject.
 

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Contents

INTRODUCTION
9
11 WHY USE A LOW SUPPLY VOLTAGE?
10
12 WHY USE BIPOLAR TECHNOLOGY?
12
13 OBJECTIVES OF THE PRESENT WORK
13
15 OUTLINE OF THIS BOOK
16
16 REFERENCES
17
INPUT STAGES
21
22 COMPLEMENTARY INPUT STAGE WITH CONSTANT TRANSCONDUCTANCE
24
47 REFERENCES
103
FREQUENCY COMPENSATION
105
51 SIMPLE MILLER COMPENSATION
106
512 Twopole Output Stage
114
52 NESTED MILLER COMPENSATION
119
521 Onepole Output Stage
120
522 Twopole Output Stage
129
53 MULTIPATHDRIVEN MILLER COMPENSATION
134

23 RAILTORAIL INPUT STAGE AT 1 VOLT
30
24 INPUT STAGE WITH EXTENDED INPUTVOLTAGE RANGE
40
25 REFERENCES
43
OUTPUT STAGES
45
31 COMMONEMITTER OUTPUT STAGE
47
22 DARLINGTON OUTPUT STAGE
51
33 WIDLAR OUTPUT STAGE
58
34 MULTIPATHDRIVEN OUTPUT STAGE
66
36 CONCLUSIONS
80
OTHER CIRCUIT PARTS
83
42 CLASSAB CURRENT CONTROLCIRCUITS
88
422 Feedback ClassAB Current Control
92
44 OUTPUTCURRENT LIMITERS
98
45 BIAS CIRCUIT
100
46 CONCLUSIONS
102
54 SLEWING
145
55 CONCLUSIONS
146
56 REFERENCES
147
REALIZATIONS
149
62 1V OPAMP IS549
157
63 OPAMPS U2010 AND U2011
167
631 Darlington Output Stage
168
632 Widlar Output Stage
169
633 MultiPathDriven Output Stage
171
634 ParallelFeedbackCurrent Compensated Output Stage
172
635 Common Circuit Parts
174
636 Measurement Results
178
64 1V OPAMP WITH 10MHz BANDWIDTH
184
65 CONCLUSIONS
192
66 REFERENCES
193

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