Low Cost, Low Power Instrumentation Amplifier AD620

134 Pages·2013·2.24 MB·English

a
Low Cost, Low Power
Instrumentation Amplifier
AD620
FEATURES CONNECTION DIAGRAM
EASY TO USE
8-Lead Plastic Mini-DIP (N), Cerdip (Q)
Gain Set with One External Resistor
and SOIC (R) Packages
(Gain Range 1 to 1000)
Wide Power Supply Range (62.3 V to 618 V)
Higher Performance than Three Op Amp IA Designs RG 1 8 RG
Available in 8-Lead DIP and SOIC Packaging –IN 2 7 +VS
Low Power, 1.3 mA max Supply Current
+IN 3 6 OUTPUT
EXCELLENT DC PERFORMANCE (“B GRADE”)
–VS 4 AD620 5 REF
50 mV max, Input Offset Voltage
0.6mV/8C max, Input Offset Drift TOP VIEW
1.0 nA max, Input Bias Current
100 dB min Common-Mode Rejection Ratio (G = 10) 1000. Furthermore, the AD620 features 8-lead SOIC and DIP
packaging that is smaller than discrete designs, and offers lower
LOW NOISE
9 nV/(cid:214) Hz, @ 1 kHz, Input Voltage Noise power (only 1.3 mA max supply current), making it a good fit
0.28 mV p-p Noise (0.1 Hz to 10 Hz) for battery powered, portable (or remote) applications.
The AD620, with its high accuracy of 40 ppm maximum
EXCELLENT AC SPECIFICATIONS nonlinearity, low offset voltage of 50m V max and offset drift of
120 kHz Bandwidth (G = 100) 0.6 m V/(cid:176) C max, is ideal for use in precision data acquisition
15 ms Settling Time to 0.01%
systems, such as weigh scales and transducer interfaces. Fur-
APPLICATIONS thermore, the low noise, low input bias current, and low power
Weigh Scales of the AD620 make it well suited for medical applications such
ECG and Medical Instrumentation as ECG and noninvasive blood pressure monitors.
Transducer Interface The low input bias current of 1.0 nA max is made possible with
Data Acquisition Systems the use of Superbeta processing in the input stage. The AD620
Industrial Process Controls works well as a preamplifier due to its low input voltage noise of
Battery Powered and Portable Equipment 9 nV/(cid:214) Hz at 1 kHz, 0.28m V p-p in the 0.1 Hz to 10 Hz band,
0.1 pA/(cid:214) Hz input current noise. Also, the AD620 is well suited
PRODUCT DESCRIPTION for multiplexed applications with its settling time of 15m s to
The AD620 is a low cost, high accuracy instrumentation ampli-
0.01% and its cost is low enough to enable designs with one in-
fier that requires only one external resistor to set gains of 1 to
amp per channel.
30,000 10,000
E
CAL 25,000 3 I NO-AP-MAPMP 1,000
OTAL ERROR, PPM OF FULL S 1125050,,,,000000000000 RAGD620A (3 OP-07s) RTI VOLTAGE NOISEm(0.1 – 10Hz) – V p-p 101010 G = 100TBINYIP-PAOIMCLPAALR SINTPAUNTDARD ABINDIP-A6O2ML0PA SRU PINEPRUbTETA
T
0 0.1
0 5 10 15 20 1k 10k 100k 1M 10M 100M
SUPPLY CURRENT – mA SOURCE RESISTANCE – V
Figure 1.Three Op Amp IA Designs vs. AD620 Figure 2.Total Voltage Noise vs. Source Resistance
REV.E
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106,U.S.A.
which may result from its use. No license is granted by implication or Tel: [phone] World Wide Web Site: http://www.analog.com
otherwise under any patent or patent rights of Analog Devices. Fax: [phone] © Analog Devices, Inc., 1999
AD620–SPECIFICATIONS
(Typical @ +258C, V = 615V, and R = 2 kV, unless otherwise noted)
S L
AD620A AD620B AD620S1
Model Conditions Min Typ Max Min Typ Max Min Typ Max Units
GAIN G = 1 + (49.4 k/R )
G
Gain Range 1 10,000 1 10,000 1 10,000
Gain Error2 V = – 10 V
OUT
G = 1 0.03 0.10 0.01 0.02 0.03 0.10 %
G = 10 0.15 0.30 0.10 0.15 0.15 0.30 %
G = 100 0.15 0.30 0.10 0.15 0.15 0.30 %
G = 1000 0.40 0.70 0.35 0.50 0.40 0.70 %
Nonlinearity, V = –10 V to +10 V,
OUT
G = 1–1000 R = 10 kW 10 40 10 40 10 40 ppm
L
G = 1–100 R = 2 kW 10 95 10 95 10 95 ppm
L
Gain vs. Temperature
G =1 10 10 10 ppm/(cid:176)C
Gain >12 –50 –50 –50 ppm/(cid:176)C
VOLTAGE OFFSET (Total RTI Error = V + V /G)
OSI OSO
Input Offset, V V = – 5 V to – 15 V 30 125 15 50 30 125 m V
OSI S
Over Temperature V = – 5 V to – 15 V 185 85 225 m V
S
Average TC V = – 5 V to – 15 V 0.3 1.0 0.1 0.6 0.3 1.0 m V/(cid:176)C
S
Output Offset, V V = – 15 V 400 1000 200 500 400 1000 m V
OSO S
V = – 5 V 1500 750 1500 m V
S
Over Temperature V = – 5 V to – 15 V 2000 1000 2000 m V
S
Average TC V = – 5 V to – 15 V 5.0 15 2.5 7.0 5.0 15 m V/(cid:176)C
S
Offset Referred to the
Input vs.
Supply (PSR) V = – 2.3 V to – 18 V
S
G = 1 80 100 80 100 80 100 dB
G = 10 95 120 100 120 95 120 dB
G = 100 110 140 120 140 110 140 dB
G = 1000 110 140 120 140 110 140 dB
INPUT CURRENT
Input Bias Current 0.5 2.0 0.5 1.0 0.5 2 nA
Over Temperature 2.5 1.5 4 nA
Average TC 3.0 3.0 8.0 pA/(cid:176)C
Input Offset Current 0.3 1.0 0.3 0.5 0.3 1.0 nA
Over Temperature 1.5 0.75 2.0 nA
Average TC 1.5 1.5 8.0 pA/(cid:176)C
INPUT
Input Impedance
Differential 10i2 10i2 10i2 GW ipF
Common-Mode 10i2 10i2 10i2 GW ipF
Input Voltage Range3 V = – 2.3 V to – 5 V –V + 1.9 +V – 1.2 –V + 1.9 +V – 1.2 –V + 1.9 +V – 1.2 V
S S S S S S S
Over Temperature –V + 2.1 +V – 1.3 –V + 2.1 +V – 1.3 –V + 2.1 +V – 1.3 V
S S S S S S
V = – 5 V to – 18 V –V + 1.9 +V – 1.4 –V + 1.9 +V – 1.4 –V + 1.9 +V – 1.4 V
S S S S S S S
Over Temperature –V + 2.1 +V – 1.4 –V + 2.1 +V – 1.4 –V + 2.3 +V – 1.4 V
S S S S S S
Common-Mode Rejection
Ratio DC to 60 Hz with
I kW Source Imbalance V = 0 V to – 10 V
CM
G = 1 73 90 80 90 73 90 dB
G = 10 93 110 100 110 93 110 dB
G = 100 110 130 120 130 110 130 dB
G = 1000 110 130 120 130 110 130 dB
OUTPUT
Output Swing R = 10 kW ,
L
V = – 2.3 V to – 5 V –V + 1.1 +V – 1.2 –V + 1.1 +V – 1.2 –V + 1.1 +V – 1.2 V
S S S S S S S
Over Temperature –V + 1.4 +V – 1.3 –V + 1.4 +V – 1.3 –V + 1.6 +V – 1.3 V
S S S S S S
V = – 5 V to – 18 V –V + 1.2 +V – 1.4 –V + 1.2 +V – 1.4 –V + 1.2 +V – 1.4 V
S S S S S S S
Over Temperature –V + 1.6 +V – 1.5 –V + 1.6 +V – 1.5 –V + 2.3 +V – 1.5 V
S S S S S S
Short Current Circuit – 18 – 18 – 18 mA
–2– REV. E
AD620
AD620A AD620B AD620S1
Model Conditions Min Typ Max Min Typ Max Min Typ Max Units
DYNAMIC RESPONSE
Small Signal –3 dB Bandwidth
G = 1 1000 1000 1000 kHz
G = 10 800 800 800 kHz
G = 100 120 120 120 kHz
G = 1000 12 12 12 kHz
Slew Rate 0.75 1.2 0.75 1.2 0.75 1.2 V/m s
Settling Time to 0.01% 10 V Step
G = 1–100 15 15 15 m s
G = 1000 150 150 150 m s
NOISE
Voltage Noise, 1 kHz T otalRTINoise= (e2ni)+(eno/G)2
Input, Voltage Noise, e 9 13 9 13 9 13 nV/(cid:214) Hz
ni
Output, Voltage Noise, e 72 100 72 100 72 100 nV/(cid:214) Hz
no
RTI, 0.1 Hz to 10 Hz
G = 1 3.0 3.0 6.0 3.0 6.0 m V p-p
G = 10 0.55 0.55 0.8 0.55 0.8 m V p-p
G = 100–1000 0.28 0.28 0.4 0.28 0.4 m V p-p
Current Noise f = 1 kHz 100 100 100 fA/(cid:214) Hz
0.1 Hz to 10 Hz 10 10 10 pA p-p
REFERENCE INPUT
R 20 20 20 kW
IN
I V , V = 0 +50 +60 +50 +60 +50 +60 m A
IN IN+ REF
Voltage Range –V + 1.6 +V – 1.6 –V + 1.6 +V – 1.6 –V + 1.6 +V – 1.6 V
S S S S S S
Gain to Output 1 – 0.0001 1 – 0.0001 1 – 0.0001
POWER SUPPLY
Operating Range4 – 2.3 – 18 – 2.3 – 18 – 2.3 – 18 V
Quiescent Current V = – 2.3 V to – 18 V 0.9 1.3 0.9 1.3 0.9 1.3 mA
S
Over Temperature 1.1 1.6 1.1 1.6 1.1 1.6 mA
TEMPERATURE RANGE
For Specified Performance –40 to +85 –40 to +85 –55 to +125 (cid:176)C
NOTES
1See Analog Devices military data sheet for 883B tested specifications.
2Does not include effects of external resistor R .
G
3One input grounded. G = 1.
4This is defined as the same supply range which is used to specify PSR.
Specifications subject to change without notice.
REV. E –3–
AD620
ABSOLUTE MAXIMUM RATINGS1 ORDERING GUIDE
SupplyVoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .– 18V
InternalPowerDissipation2 . . . . . . . . . . . . . . . . . . . . .650 mW Model Temperature Ranges Package Options*
Input Voltage (Common Mode) . . . . . . . . . . . . . . . . . . . . – VS AD620AN –40(cid:176) C to +85(cid:176) C N-8
DifferentialInputVoltage . . . . . . . . . . . . . . . . . . . . . . . .– 25V AD620BN –40(cid:176) C to +85(cid:176) C N-8
Output Short Circuit Duration . . . . . . . . . . . . . . . . .Indefinite AD620AR –40(cid:176) C to +85(cid:176) C SO-8
Storage Temperature Range (Q) . . . . . . . . . .–65(cid:176) C to +150(cid:176) C AD620AR-REEL –40(cid:176) C to +85(cid:176) C 13" REEL
Storage Temperature Range (N, R) . . . . . . . .–65(cid:176) C to +125(cid:176) C AD620AR-REEL7 –40(cid:176) C to +85(cid:176) C 7" REEL
Operating Temperature Range AD620BR –40(cid:176) C to +85(cid:176) C SO-8
AD620 (A, B) . . . . . . . . . . . . . . . . . . . . . . –40(cid:176) C to +85(cid:176) C AD620BR-REEL –40(cid:176) C to +85(cid:176) C 13" REEL
AD620 (S) . . . . . . . . . . . . . . . . . . . . . . . . –55(cid:176) C to +125(cid:176) C AD620BR-REEL7 –40(cid:176) C to +85(cid:176) C 7" REEL
Lead Temperature Range AD620ACHIPS –40(cid:176) C to +85(cid:176) C Die Form
(Soldering10seconds) . . . . . . . . . . . . . . . . . . . . . . . +300(cid:176) C AD620SQ/883B –55(cid:176) C to +125(cid:176) C Q-8
NOTES
*N = Plastic DIP; Q = Cerdip; SO = Small Outline.
1Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
2Specification is for device in free air:
8-Lead Plastic Package: q = 95(cid:176)C/W
JA
8-Lead Cerdip Package: q = 110(cid:176)C/W
JA
8-Lead SOIC Package: q = 155(cid:176)C/W
JA
METALIZATION PHOTOGRAPH
Dimensions shown in inches and (mm).
Contact factory for latest dimensions.
RG* +VS OUTPUT
8 7 6
5 REFERENCE
8
0.0708
(1.799)
1
1 2 3 4
RG* (03..112850) –VS
–IN +IN
*FOR CHIP APPLICATIONS: THE PADS 1RG AND 8RG MUST BE CONNECTED IN PARALLEL
TO THE EXTERNAL GAIN REGISTER RG. DO NOT CONNECT THEM IN SERIES TO RG. FOR
UNITY GAIN APPLICATIONS WHERE RG IS NOT REQUIRED, THE PADS 1RG MAY SIMPLY
BE BONDED TOGETHER, AS WELL AS THE PADS 8RG.
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily WARNING!
accumulate on the human body and test equipment and can discharge without detection.
Although the AD620 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
ESD SENSITIVE DEVICE
precautions are recommended to avoid performance degradation or loss of functionality.
–4– REV. E
AD620
Typical Characteristics
(@ +258C, V = 615 V, R = 2 kV, unless otherwise noted)
S L
50 2.0
SAMPLE SIZE = 360
1.5
40
S A 1.0
NIT – n +IB
E OF U 30 RRENT 0.5 –IB
AG CU 0
CENT 20 BIAS –0.5
PER PUT
N–1.0
10 I
–1.5
0
–2.0
–80 –40 0 +40 [phone] 175
INPUT OFFSET VOLTAGE – mV TEMPERATURE – 8C
Figure 3.Typical Distribution of Input Offset Voltage Figure 6.Input Bias Current vs. Temperature
50 2
SAMPLE SIZE = 850
V
40 m–
E 1.5
S G
NIT TA
GE OF U30 SET VOL 1
A F
NT20 OF
PERCE NGE IN 0.5
10 A
H
C
0
0
–1200 –600 0 +600 [phone]
INPUT BIAS CURRENT – pA WARM-UP TIME – Minutes
Figure 4.Typical Distribution of Input Bias Current Figure 7.Change in Input Offset Voltage vs.
Warm-Up Time
50 1000
SAMPLE SIZE = 850
40 GAIN = 1
S
NIT Hz100
TAGE OF U30 !OISE – nV/ GAIN = 10
PERCEN20 LTAGE N 10
10 VO
GAIN = 100, 1,000
GAIN = 1000
BW LIMIT
0 1
–400 –200 0 +200 +400
1 10 100 1k 10k 100k
INPUT OFFSET CURRENT – pA FREQUENCY – Hz
Figure 5.Typical Distribution of Input Offset Current Figure 8.Voltage Noise Spectral Density vs. Frequency,
(G = 1–1000)
REV. E –5–
AD620–Typical Characteristics
1000
Hz
!A/
– f
E
OIS100
N
T
N
E
R
R
U
C
10
1 10 100 1000
FREQUENCY – Hz
Figure 9.Current Noise Spectral Density vs. Frequency Figure 11.0.1 Hz to 10 Hz Current Noise, 5 pA/Div
100,000
V
m
–
TI
V C, R10,000
DI 85
mSE – 2.0 V/ 8M 25C TO 8 1000 FINE-TA MINPPUT
RTI NOI FT FRO AD620A
RI 100
D
L
A
T
O
T
10
TIME – 1 SEC/DIV 1k 10k 100k 1M 10M
SOURCE RESISTANCE – V
Figure 10a.0.1 Hz to 10 Hz RTI Voltage Noise (G = 1) Figure 12.Total Drift vs. Source Resistance
+160
+140 G = 1000
G = 100
+120
V
DI G = 10
V/ +100
m
SE – 0.1 MR – dB +80 G = 1
OI C
N +60
TI
R
+40
+20
0
TIME – 1 SEC/DIV 0.1 1 10 100 1k 10k 100k 1M
FREQUENCY – Hz
Figure 13.CMR vs. Frequency, RTI, Zero to 1 kW Source
Figure 10b.0.1 Hz to 10 Hz RTI Voltage Noise (G = 1000)
Imbalance
–6– REV. E
AD620
180 35
G = 10, 100, 1000
160
30
p
140 G = 1000 olts p- 25
120 – V G = 1
B E 20
d G
PSR – 18000 G = 100 T VOLTA 15 LIMIT
60 G = 10 UTPU 10 BW
O
40 G = 1 5
G = 1000
G = 100
20 0
0.1 1 10 100 1k 10k 100k 1M 1k 10k 100k 1M
FREQUENCY – Hz FREQUENCY – Hz
Figure 14.Positive PSR vs. Frequency, RTI (G = 1–1000) Figure 17.Large Signal Frequency Response
180 +VS –0.0
160 –0.5
S)
E
sG
140 – VoltOLTA –1.0
120 MIT Y V –1.5
– dB100 GE LIUPPL
PSR 80 G = 1000 VOLTAD TO S +1.5
60 GG == 11000 INPUT EFERRE +1.0
R
40 ( +0.5
G = 1
20 –VS +0.0
0.1 1 10 100 1k 10k 100k 1M 0 5 10 15 20
FREQUENCY – Hz SUPPLY VOLTAGE 6 Volts
Figure 15.Negative PSR vs. Frequency, RTI (G = 1–1000) Figure 18.Input Voltage Range vs. Supply Voltage, G = 1
1000 +VS –0.0
–0.5
100 VoltsAGES) –1.0 RL = 10kV
NG – VOLT –1.5 RL = 2kV
GAIN – V/V 110 OUTPUT VOLTAGE SWI(REFERRED TO SUPPLY +++101...055 RL = 10RkLV = 2kV
0.1 –VS +0.0
100 1k 10k 100k 1M 10M 0 5 10 15 20
FREQUENCY – Hz SUPPLY VOLTAGE 6 Volts
Figure 16.Gain vs. Frequency Figure 19.Output Voltage Swing vs. Supply Voltage,
G = 10
REV. E –7–
AD620
30
p
s p- VS = 615V ........................................
olt G = 10
V
– 20
G
N
WI
S
E
G
A
T
L
O 10
V
T
U ........................................
P
T
U
O
0
0 100 1k 10k
LOAD RESISTANCE – V
Figure 20.Output Voltage Swing vs. Load Resistance Figure 23.Large Signal Response and Settling Time,
G = 10 (0.5 mV = 001%)
........................................ ........................................
........................................ ........................................
Figure 21.Large Signal Pulse Response and Settling Time Figure 24.Small Signal Response, G = 10, R = 2kW ,
L
G = 1 (0.5 mV = 0.01%) C = 100 pF
L
........................................ ........................................
........................................ ........................................
Figure 22.Small Signal Response, G = 1, R = 2 kW , Figure 25.Large Signal Response and Settling Time,
L
C = 100 pF G = 100 (0.5 mV = 0.01%)
L
–8– REV. E
AD620
20
........................................
15
TO 0.01%
s
m
– TO 0.1%
E
M
G TI 10
N
LI
T
T
E
S
........................................ 5
0
0 5 10 15 20
OUTPUT STEP SIZE – Volts
Figure 26.Small Signal Pulse Response, G = 100, Figure 29.Settling Time vs. Step Size (G = 1)
R = 2 kW , C = 100 pF
L L
1000
........................................
s
m– 100
E
M
TI
G
N
LI
T
T
SE 10
........................................
1
1 10 100 1000
GAIN
Figure 27.Large Signal Response and Settling Time, Figure 30.Settling Time to 0.01% vs. Gain, for a 10 V Step
G = 1000 (0.5 mV = 0.01%)
........................................ ........................................

........................................ ........................................
Figure 28.Small Signal Pulse Response, G = 1000, Figure 31a.Gain Nonlinearity, G = 1, R = 10 kW
L
RL = 2 kW , CL = 100 pF (10 m V = 1 ppm)
REV. E –9–
AD620
I1 20mA VB 20mA I2
........................................
A1 A2 10kV
C1 C2
10kV
A3 OUTPUT
R3 R1 R2 10kV 10kV REF
400V
– IN Q1 Q2 +IN
R4
........................................ RG 400V
GAIN GAIN
SENSE SENSE
–VS
Figure 33. Simplified Schematic of AD620
Figure 31b.Gain Nonlinearity, G = 100, R = 10 kW
L
(100m V = 10 ppm) THEORY OF OPERATION
The AD620 is a monolithic instrumentation amplifier based on
a modification of the classic three op amp approach. Absolute
value trimming allows the user to program gain accurately (to
0.15% at G = 100) with only one resistor. Monolithic construc-
tion and laser wafer trimming allow the tight matching and
........................................ tracking of circuit components, thus ensuring the high level of
performance inherent in this circuit.
The input transistors Q1 and Q2 provide a single differential-
pair bipolar input for high precision (Figure 33), yet offer 10·
lower Input Bias Current thanks to Superbeta processing. Feed-
back through the Q1-A1-R1 loop and the Q2-A2-R2 loop main-
tains constant collector current of the input devices Q1, Q2
........................................ thereby impressing the input voltage across the external gain
setting resistor R . This creates a differential gain from the
G
inputs to the A1/A2 outputs given by G = (R1 + R2)/R + 1.
G
The unity-gain subtracter A3 removes any common-mode sig-
nal, yielding a single-ended output referred to the REF pin
potential.
Figure 31c.Gain Nonlinearity, G = 1000, R = 10kW
L The value of R also determines the transconductance of the
G
(1mV = 100ppm)
preamp stage. As R is reduced for larger gains, the transcon-
G
ductance increases asymptotically to that of the input transistors.
1kV This has three important advantages: (a) Open-loop gain is
10kV* 10T 10kV
INPUT boosted for increasing programmed gain, thus reducing gain-
10V p-p
100kV related errors. (b) The gain-bandwidth product (determined by
VOUT C1, C2 and the preamp transconductance) increases with pro-
grammed gain, thus optimizing frequency response. (c) The
+VS input voltage noise is reduced to a value of 9 nV/(cid:214) Hz, deter-
11kV 1kV 100V 2 mined mainly by the collector current and base resistance of the
1 7
input devices.
G=1000 G=1
G=100 G=10 AD620 6 Tluhtee vinaltueren oafl 2g4ai.n7 rkeWsi,s atollrosw, Rin1g athned gRa2in, atore b ter imprmogerda mtom aend abso-
49.9V 499V 5.49kV 5 accurately with a single external resistor.
8
4 The gain equation is then
3
–VS G= 49.4kW +1
*ALL RESISTORS 1% TOLERANCE
R
G
Figure 32.Settling Time Test Circuit
so that
49.4kW
R =
G G- 1

–10– REV. E