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AD626

Low Cost, Single-Supply

Differential Ampliﬁ er

FEATURES

Pin Selectable Gains of 10 and 100

Tr ue Single-Supply Operation

Single-Supply Range of +2.4 V to +10 V

Dual-Supply Range of ⴞ1.2 V to ⴞ6 V

Wide Output Voltage Range of 30 mV to 4.7 V

Optional Low-Pass Filtering

Excellent DC Performance

Low Input Offset Voltage: 500 ␮V Max

Large Common-Mode Range: 0 V to +54 V

Low Power: 1.2 mW (V

= +5 V)

Good CMR of 90 dB Typ

AC Performance

Fast Settling Time: 24 ␮s (0.01%)

Includes Input Protection

Series Resistive Inputs (R

= 200 k⍀)

RFI Filters Included

Allows 50 V Continuous Overload

APPLICATIONS

Current Sensing

Interface for Pressure Transducers, Position Indicators,

Strain Gages, and Other Low Level Signal Sources

PROD UCT DE SCRIP TION

The AD626 is a low cost, true sin gle-sup ply dif fer en tial am pli ﬁ er

de signed for am pli fy ing and low-pass ﬁ ltering small dif fer en tial

voltages from sources having a large common-mode voltage.

The AD626 can operate from either a single supply of +2.4 V to

+10 V, or dual supplies of ±1.2 V to ±6 V. The input common-mode

range of this ampliﬁ er is equal to 6 (+V

– 1 V) which pro vides a

+24 V CMR while operating from a +5 V sup ply. Fur ther more,

the AD626 features a CMR of 90 dB typ.

The ampliﬁ er’s inputs are protected against continuous overload of

up to 50 V, and RFI ﬁ lters are included in the attenuator network.

The output range is +0.03 V to +4.9 V using a +5 V sup ply. The

ampliﬁ er provides a preset gain of 10, but gains be tween 10 and

100 can be easily con ﬁ g ured with an external re sis tor. Fur ther -

more, a gain of 100 is available by connecting the G = 100 pin to

analog ground. The AD626 also offers low-pass ﬁ lter capability by

connecting a ca pac i tor between the ﬁ lter pin and analog ground.

The AD626A and AD626B operate over the industrial tem per a ture

range of –40°C to +85°C. The AD626 is available in two 8-lead

packages: a plastic mini-DIP and SOIC.

140

0.1

120

100

100k10k 1k100 10

FREQUENCY – Hz

COMMON-MODE REJECTION – dB

G = 10, 100

= +5V

G = 100

= ⴞ5V

G = 10

= ⴞ5V

Figure 1. Common-Mode Rejection vs. Frequency

SUPPLY VOLTAGE – ⴞV

INPUT COMMON-MODE RANGE – V

ⴞV

FOR SINGLE

AND DUAL SUPPLIES

ⴞV

FOR DUAL

SUPPLIES ONLY

Figure 2. Input Common-Mode Range vs. Supply

CONNECTION DIAGRAM

8-Lead Plastic Mini-DIP (N)

and SOIC (R) Packages

AD626

1/6

200k⍀

–IN

ANALOG

GND

–V

FILTER

+IN

G = 100

OUT

100k⍀

G = 30

200k⍀

REV. D

Summary of content (13 pages)

PAGE 1
Low Cost, Single-Supply Differential Amplifier AD626 FEATURES Pin Selectable Gains of 10 and 100 True Single-Supply Operation Single-Supply Range of +2.4 V to +10 V Dual-Supply Range of ⴞ1.2 V to ⴞ6 V Wide Output Voltage Range of 30 mV to 4.7 V Optional Low-Pass Filtering Excellent DC Performance Low Input Offset Voltage: 500 ␮V Max Large Common-Mode Range: 0 V to +54 V Low Power: 1.2 mW (VS = +5 V) Good CMR of 90 dB Typ AC Performance Fast Settling Time: 24 ␮s (0.
PAGE 2
Powered by TCPDF (www.tcpdf.org) IMPORTANT LINKS for the AD626* Last content update 09/10/2013 07:55 pm Newer Alternatives: AD8276 or the AD8278 difference amps for their faster speed, smaller foot print, wider supply voltage range, and lower costs. PARAMETRIC SELECTION TABLES DESIGN COLLABORATION COMMUNITY Find Similar Products By Operating Parameters Collaborate Online with the ADI support team and other designers about select ADI products.
PAGE 3
AD626–SPECIFICATIONS SINGLE SUPPLY (@+VS = +5 V and TA = 25ⴗC, unless otherwise noted.) Model Parameter GAIN Gain Accuracy Gain = 10 Gain = 100 Over Temperature, TA = TMIN to TMAX Gain Linearity Gain = 10 Gain = 100 OFFSET VOLTAGE Input Offset Voltage vs. Temperature vs. Temperature vs.
PAGE 4
AD626 DUAL SUPPLY (@+VS = ⴞ5 V and TA = 25ⴗC, unless otherwise noted.
PAGE 5
AD626 ABSOLUTE MAXIMUM RATINGS1 NOTES 1 Stresses above those listed under Absolute Maximum Ratings may cause permanent 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. 2 8-Lead Plastic Package: ␪JA = 100°C/W; ␪JC = 50°C/W.
PAGE 6
Typical Performance Characteristics–AD626 6 VS = ⴞ5V GAIN = 10, 100 5 POSITIVE OUTPUT VOLTAGE – V INPUT COMMON-MODE RANGE – V 25 20 ⴞVCM FOR SINGLE AND DUAL SUPPLIES 15 10 ⴞVCM FOR DUAL SUPPLIES ONLY 5 0 4 3 2 1 0 –1 1 2 3 4 5 10 100 1k LOAD RESISTANCE – ⍀ SUPPLY VOLTAGE – ⴞV TPC 1. Input Common-Mode Range vs. Supply TPC 4. Positive Output Voltage Swing vs.
PAGE 7
AD626 100 COMMON-MODE REJECTION – dB 1000 VS = ⴞ5V DUAL SUPPLY CLOSED-LOOP GAIN GAIN = 100 100 VS = +5V SINGLE SUPPLY GAIN = 10 10 VS = ⴞ5V DUAL SUPPLY 0 10 100 90 85 80 VS = ⴞ5 75 70 1k 10k FREQUENCY – Hz 100k 65 20 1M TPC 7. Closed-Loop Gain vs. Frequency 22 24 26 28 INPUT COMMON-MODE VOLTAGE – V 30 TPC 10. Common-Mode Rejection vs.
PAGE 8
AD626 2␮V PER VERTICAL DIVISION QUIESCENT CURRENT – mA 0.16 0.15 G = 10 0.14 0.13 0.12 1 2 3 SUPPLY VOLTAGE – V 4 5 5 SECONDS PER HORIZONTAL DIVISION TPC 13. Quiescent Supply Current vs. Supply Voltage for Single-Supply Operation TPC 16. 0.1 Hz to 10 Hz RTI Voltage Noise. VS = ±5 V, Gain = 100 100 80 1.5 CLOSED-LOOP GAIN QUIESCENT CURRENT – mA 2.0 1.0 FOR VS = ⴞ5V AND +5V 60 40 0.5 20 0 ⴞ1 ⴞ2 ⴞ3 SUPPLY VOLTAGE – V ⴞ4 0 ⴞ5 1 TPC 14. Quiescent Supply Current vs.
PAGE 9
AD626 100 100 90 90 10 10 0% 0% TPC 19. Large Signal Pulse Response. VS = ±5 V, G = 10 TPC 22. Large Signal Pulse Response. VS = +5 V, G = 100 100 100 90 90 10 10 0% 0% TPC 20. Large Signal Pulse Response. VS = ±5 V, G = 100 TPC 23. Settling Time. VS = ±5 V, G = 10 500mV 100 100 90 90 10 10 0% 0% TPC 21. Large Signal Pulse Response. VS = +5 V, G = 10 TPC 24. Settling Time. VS = ±5 V, G = 100 –8– REV.
PAGE 10
AD626 100 100 90 90 10 10 0% 0% TPC 25. Settling Time. VS = +5 V, G = 10 TPC 26. Settling Time. VS = +5 V, G = 100 Figure 4 shows the main elements of the AD626. The signal inputs at Pins 1 and 8 are first applied to dual resistive attenuators R1 through R4 whose purpose is to reduce the peak common-mode voltage at the input to the preamplifier—a feedback stage based on the very low drift op amp A1.
PAGE 11
AD626 necessary to minimize gain error. Also, any mismatch between the total source resistance at each input will affect gain accuracy and common-mode rejection (CMR). For example: when operating at a gain of 10, an 80 ⍀ mismatch in the source resistance between the inputs will degrade CMR to 68 dB. +INPUT –INPUT 200k⍀ –IN 200k⍀ +IN 2 –VS 3 ANALOG GND G = 100 7 G = 30 –VS +VS +VS 6 100k⍀ 0.1␮F The output of amplifier A2 relies on a 10 k⍀ resistor to –VS for “pull-down.
PAGE 12
AD626 CURRENT SENSOR INTERFACE BRIDGE APPLICATION A typical current sensing application, making use of the large common-mode range of the AD626, is shown in Figure 9. The current being measured is sensed across resistor RS. The value of RS should be less than 1 k⍀ and should be selected so that the average differential voltage across this resistor is typically 100 mV. Figure 10 shows the AD626 in a typical bridge application.
PAGE 13
AD626 OUTLINE DIMENSIONS 8-Lead Standard Small Outline Package [SOIC] Narrow Body (R-8) C00781–0–1/03(D) Dimensions shown in millimeters and (inches) 5.00 (0.1968) 4.80 (0.1890) 4.00 (0.1574) 3.80 (0.1497) 8 5 1 4 6.20 (0.2440) 5.80 (0.2284) 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY SEATING 0.10 PLANE 0.50 (0.0196) ⴛ45ⴗ 0.25 (0.0099) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.33 (0.0130) 8ⴗ 0.25 (0.0098) 0ⴗ 1.27 (0.0500) 0.41 (0.0160) 0.19 (0.