INA121 FET-Input, Power INSTRUMENTATION AMPLIFIER FEATURES

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INA121 FET-Input, Power INSTRUMENTATION AMPLIFIER FEATURES

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INA121
FET-Input, Power INSTRUMENTATION AMPLIFIER
FEATURES
BIAS CURRENT: ±4pA QUIESCENT CURRENT: ±450µA INPUT OFFSET VOLTAGE: ±200µV INPUT OFFSET DRIFT: ±2µV/°C INPUT NOISE: 20nV/Hz 1kHz =100) HIGH CMR: 106dB WIDE SUPPLY RANGE: ±2.25V ±18V NONLINEARITY ERROR: 0.001% INPUT PROTECTION ±40V 8-PIN SO-8 SURFACE MOUNT
DESCRIPTION
INA121 FET-input, power instrumentation amplifier offering excellent accuracy. versatile three-op design very small size make ideal variety general purpose applications. bias current (±4pA) allows with high impedance sources. Gain from 10,000V/V with single external resistor. Internal input protection withstand ±40V without damage. INA121 laser-trimmed very offset voltage (±200µV), offset drift (±2µV/°C), high common-mode rejection (106dB 100). operates power supplies ±2.25V (+4.5V), allowing battery operated single systems. Quiescent current only 450µA. Package options include 8-pin plastic SO-8 surface mount. specified -40°C +85°C industrial temperature range.
APPLICATIONS
LOW-LEVEL TRANSDUCER AMPLIFIERS Bridge, RTD, Thermocouple PHYSIOLOGICAL AMPLIFIERS ECG, EEG, EMG, Respiratory HIGH IMPEDANCE TRANSDUCERS CAPACITIVE SENSORS MULTI-CHANNEL DATA ACQUISITION PORTABLE, BATTERY OPERATED SYSTEMS GENERAL PURPOSE INSTRUMENTATION
INA121
Over-Voltage Protection
G=1+
Over-Voltage Protection
International Airport Industrial Park Mailing Address: 11400, Tucson, 85734 Street Address: 6730 Tucson Blvd., Tucson, 85706 Tel: (520) 746-1111 Twx: 910-952-1111 Internet: http://www.burr-brown.com/ FAXLine: (800) 548-6133 (US/Canada Only) Cable: BBRCORP Telex: 066-6491 FAX: (520) 889-1510 Immediate Product Info: (800) 548-6132
©1997 Burr-Brown Corporation
PDS-1412A
INA121
Printed U.S.A. May, 1998
SPECIFICATIONS: ±15V
+25°C, ±15V, 10k, reference unless otherwise noted. INA121P, PARAMETER INPUT Offset Voltage, Temperature Power Supply Long-Term Stability Impedance, Differential Common-Mode Input Voltage Range Safe Input Voltage Common-Mode Rejection CONDITIONS INA121PA, UNITS µV/°C µV/V µV/mo
±2.25V ±18V
±200±200/G ±500±500/G ±2±2/G ±5±20/G ±5±20/G ±50±150/G ±0.5 1012 1012 Text Typical Curves Typical Curve ±0.5 Typical Curve (50k/RG) 10,000 ±0.01 ±0.03 ±0.05 ±0.5 ±0.0002 ±0.0015 ±0.0015 ±0.002 (V+)-0.9 (V-)+0.15 (V+)-0.9 (V-)+0.25 1000 ±2.25 ±450 ±525 ±0.05 ±0.4 ±0.5 ±100 ±0.001 ±0.005 ±0.005
±300±200/G ±1000±1000/G ±15±20/G ±0.1 ±0.5 ±0.7 ±0.002 ±0.008 ±0.008
-12.5V 13.5V 1000
BIAS CURRENT Temperature Offset Current Temperature NOISE, Voltage Noise: 10Hz 100Hz 1kHz 0.1Hz 10Hz Current Noise: 1kHz GAIN Gain Equation Range Gain Gain Error
nV/Hz nV/Hz nV/Hz µVp-p fA/Hz ppm/°C ppm/°C
Gain Temperature(1) Nonlinearity
-14V 13.5V 1000 -14V 13.5V 1000 100k 100k
OUTPUT Voltage: Positive Negative Positive Negative Capacitance Load Drive Short-Circuit Current FREQUENCY RESPONSE Bandwidth, -3dB
(V+)-1.5 (V-)+1
V/µs °C/W °C/W
Slew Rate Settling Time, 0.01%
Overload Recovery POWER SUPPLY Voltage Range Quiescent Current TEMPERATURE RANGE Specification Operating Storage Thermal Resistance, 8-Lead SO-8 Surface Mount Specification same INA121P,
1000 ±10V, 1000 Input Overload
NOTE: Temperature coefficient "Internal Resistor" gain equation. Does include gain-setting resistor,
INA121
CONFIGURATION
View 8-Pin SO-8
ELECTROSTATIC DISCHARGE SENSITIVITY
This integrated circuit damaged ESD. Burr-Brown recommends that integrated circuits handled with appropriate precautions. Failure observe proper handling installation procedures cause damage. damage range from subtle performance degradation complete device failure. Precision integrated circuits more susceptible damage because very small parametric changes could cause device meet published specifications.
View V-IN
ABSOLUTE MAXIMUM RATINGS(1)
Supply Voltage ±18V Analog Input Voltage Range ±40V Output Short-Circuit ground) Continuous Operating Temperature -55°C +125°C Storage Temperature -55°C +125°C Junction Temperature +150°C Lead Temperature (soldering, 10s) +300°C NOTE: Stresses above these ratings cause permanent damage. Exposure absolute maximum conditions extended periods degrade device reliability.
PACKAGE/ORDERING INFORMATION
PACKAGE DRAWING NUMBER(1) SPECIFIED TEMPERATURE RANGE -40°C +85°C -40°C +85°C -40°C +85°C -40°C +85°C PACKAGE MARKING INA121P INA121PA INA121U INA121UA ORDERING NUMBER(2) INA121P INA121PA INA121U INA121U/2K5 INA121UA INA121UA/2K5 TRANSPORT MEDIA Rails Rails Rails Tape Reel Rails Tape Reel
PRODUCT Single INA121P INA121PA INA121U INA121UA
PACKAGE 8-Pin 8-Pin SO-8 Surface-Mount SO-8 Surface-Mount
NOTES: detailed drawing dimension table, please data sheet, Appendix Burr-Brown Data Book. Models with slash available only Tape Reel quantities indicated (e.g., /2K5 indicates 2500 devices reel). Ordering 2500 pieces "INA121U/2K5" will single 2500-piece Tape Reel. detailed Tape Reel mechanical information, refer Appendix Burr-Brown Data Book.
information provided herein believed reliable; however, BURR-BROWN assumes responsibility inaccuracies omissions. BURR-BROWN assumes responsibility this information, such information shall entirely user's risk. Prices specifications subject change without notice. patent rights licenses circuits described herein implied granted third party. BURR-BROWN does authorize warrant BURR-BROWN product life support devices and/or systems.
INA121
TYPICAL PERFORMANCE CURVES
+25°C, ±15V, unless otherwise noted.
GAIN FREQUENCY
COMMON-MODE REJECTION FREQUENCY
Common-Mode Rejection (dB)
1000V/V
1000V/V 100V/V
100V/V
Gain (dB)
100k Frequency (Hz) 1V/V 10V/V
10V/V 1V/V 100k
Frequency (Hz)
POSITIVE POWER SUPPLY REJECTION FREQUENCY
NEGATIVE POWER SUPPLY REJECTION FREQUENCY 1000V/V 100V/V
Power Supply Rejection (dB)
100k Frequency (Hz) 1000V/V 100V/V 10V/V
Power Supply Rejection (dB)
10V/V 100k Frequency (Hz) 1V/V
1V/V
INPUT COMMON-MODE RANGE OUTPUT VOLTAGE, ±15V
INPUT COMMON-MODE RANGE OUTPUT VOLTAGE, ±5V, ±2.5V
Common-Mode Voltage
Common-Mode Voltage
±2.5V
+15V
VD/2 VD/2
-15V
Output Voltage
Output Voltage
INA121
TYPICAL PERFORMANCE CURVES
+25°C, ±15V, unless otherwise noted.
(CONT)
INPUT BIAS CURRENT TEMPERATURE
Bias Current (pA)
Input Bias Current
100µ -10µ -100µ
INPUT BIAS CURRENT COMMON-MODE INPUT VOLTAGE
0.01
Common-Mode Voltage
Temperature (°C)
INPUT OVER-VOLTAGE CHARACTERISTICS
Input Current (mA)
SETTLING TIME GAIN 1000
1V/V
Settling Time (µs)
-0.2 -0.4 -0.6 -0.8
Flat region represents normal linear operation.
1000V/V
0.01% 0.1%
+15V 1V/V 1000V/V -15V
Gain (V/V)
1000
Input Voltage
QUIESCENT CURRENT SLEW RATE TEMPERATURE
SHORT-CIRCUIT CURRENT TEMPERATURE
Quiescent Current (µA)
Short-Circuit Current (µA)
+ISC
Slew Rate (V/µs)
-ISC
Temperature (°C)
Temperature (°C)
INA121
TYPICAL PERFORMANCE CURVES
+25°C, ±15V, unless otherwise noted.
(CONT)
OUTPUT VOLTAGE SWING OUTPUT CURRENT (V+) -0.3 +85°C +25°C -40°C, -55°C +125°C
MAXIMUM OUTPUT VOLTAGE FREQUENCY
Peak-to-Peak Output Voltage (Vp-p)
Output Voltage Swing
(V+) -0.6 (V+) -0.9 (V+) -1.2 (V+) -1.5 (V-) +1.5 (V-) +1.2 (V-) +0.9 (V-) +0.6 (V-) +0.3 (V-) +125°C +85°C
1000
+25°C -40°C, -55°C
Frequency (Hz)
100k
Output Current (mA)
INPUT OFFSET VOLTAGE WARM-UP
Offset Voltage Change (µV)
Percent Units
INPUT OFFSET VOLTAGE DRIFT PRODUCTION DISTRIBUTION Typical production distribution packaged units.
Time (µs)
Offset Voltage Drift (µV/°C)
INPUT-REFERRED NOISE VOLTAGE FREQUENCY 1000
VOLTAGE NOISE 10Hz INPUT-REFERRED,
Voltage Noise (nV/Hz)
1000 Limit)
Frequency (Hz)
0.5µV
/div
INA121
TYPICAL PERFORMANCE CURVES
+25°C, ±15V, unless otherwise noted.
(CONT)
SMALL-SIGNAL STEP RESPONSE
SMALL-SIGNAL STEP RESPONSE 100, 1000)
50mV/div
50mV/div
1000
10µs/div
100µs/div
LARGE-SIGNAL STEP RESPONSE
LARGE-SIGNAL STEP RESPONSE 100, 1000)
5V/div
5V/div
1000
100µs/div
100µs/div
INA121
APPLICATION INFORMATION
Figure shows basic connections required operation INA121. Applications with noisy high impedance power supplies require decoupling capacitors close device pins shown. output referred output reference (Ref) terminal which normally grounded. This must low-impedance connection assure good common-mode rejection. resistance series with will cause typical device degrade approximately 80dB SETTING GAIN Gain INA121 connecting single external resistor, connected between pins
term Equation comes from internal feedback resistors These on-chip metal film resistors laser trimmed accurate absolute values. accuracy temperature coefficient these resistors included gain accuracy drift specifications INA121. stability temperature drift external gain setting resistor, also affects gain. RG's contribution gain accuracy drift directly inferred from gain equation (1). resistor values required high gain make wiring resistance important. Sockets wiring resistance which will contribute additional gain error (possibly unstable gain error) gains approximately greater. DYNAMIC PERFORMANCE typical performance curve "Gain Frequency" shows that, despite quiescent current, INA121 achieves wide bandwidth, even high gain. This current-feedback topology INA121. Settling time also remains excellent high gain.
Commonly used gains resistor values shown Figure
0.1µF
Over-Voltage Protection INA121
(VIN VIN)
DESIRED GAIN 1000 2000 5000 10000
50.00k 12.50k 5.556k 2.632k 1.02k 505.1 251.3 100.2 50.05 25.01 10.00 5.001
NEAREST 49.9k 12.4k 5.62k 2.61k 1.02k 49.9 24.9 4.99
G=1+
Load
Over-Voltage Protection
0.1µF
Connection.
Also drawn simplified form: INA121
FIGURE Basic Connections.
INA121
INA121 provides excellent rejection high frequency common-mode signals. typical performance curve, "Common-Mode Rejection Frequency" shows this behavior. inputs properly balanced, however, common-mode signals converted differential sig- nals. connections directly adjacent each other, from source signal input pins. possible ground plane under both input traces. Avoid running other potentially noisy lines near inputs. NOISE ACCURACY PERFORMANCE INA121's input circuitry provides input bias current high speed. achieves lower noise higher accuracy with high impedance sources. With source impedances INA114, INA128, INA129 provide lower offset voltage drift. very source impedance (1k), INA103 provide improved accuracy lower noise. very high source impedances INA116 recommended. OFFSET TRIMMING INA121 laser trimmed offset voltage drift. Most applications require external offset adjustment. Figure shows optional circuit trimming output offset voltage. voltage applied terminal summed output. buffer provides impedance terminal preserve good commonmode rejection. Trim circuits with higher source impedance should buffered with follower circuit assure impedance pin.
Input circuitry must provide path this input bias current INA121 operate properly. Figure shows various provisions input bias current path. Without bias current return path, inputs will float potential which exceeds common-mode range INA121 input amplifiers will saturate. differential source resistance low, bias current return path connected input (see thermocouple example Figure With higher source impedance, using resistors provides balanced input with possible advantages lower input offset voltage bias current better high-frequency common-mode rejection.
Crystal Ceramic Transducer
INA121
Thermocouple
INA121
INA121
INA121
100µA REF200
Center-tap provides bias current return.
INA121
OPA277 ±10mV Adjustment Range 10k(1)
100(1)
VREF
Bridge
100(1)
Bridge resistance provides bias current return.
NOTE: wider trim range required high gains, scale resistor values larger
100µA REF200
FIGURE Providing Input Common-Mode Current Path. INPUT COMMON-MODE RANGE linear input voltage range input circuitry INA121 from approximately 1.2V below positive supply voltage 2.1V above negative supply. differential input voltage causes output voltage increase. linear input range, however, will limited output voltage swing amplifiers linear common-mode input range related output voltage complete amplifier. This behavior also depends supply voltage-see typical performance curve "Input Common-Mode Range Output Voltage".
FIGURE Optional Trimming Output Offset Voltage. INPUT BIAS CURRENT RETURN PATH input impedance INA121 extremely high- approximately 1012. However, path must provided input bias current both inputs. This input bias current typically 4pA. High input impedance means that this input bias current changes very little with varying input voltage.
INA121
combination common-mode differential input voltage cause output saturate. Figure shows output voltage swing expressed terms common-mode differential input voltages. applications where input common-mode range must maximized, limit output voltage swing connecting INA121 lower gain (see performance curve "Input Common-Mode Voltage Range Output Voltage"). necessary, gain after INA121 increase voltage swing. Input-overload produce output voltage that appears normal. example, input overload condition drives both input amplifiers their positive output swing limit, difference voltage measured output amplifier will near zero. output will near even though both inputs overloaded. VOLTAGE OPERATION INA121 operated power supplies ±2.25V. Performance remains excellent with power supplies ranging from ±2.25V ±18V. Most parameters vary only slightly throughout this supply voltage range-see typical
performance curves. Operation very supply voltage requires careful attention assure that input voltages remain within their linear range. Voltage swing requirements internal nodes limit input common-mode range with power supply voltage. Typical performance curves, "Input Common-Mode Range Output Voltage" show range linear operation ±15V, ±5V, ±2.5V supplies. INPUT FILTERING INA121's input allows input filter without creating large offsets input bias current. Figure shows proper implementation this input filter preserve INA121's excellent high frequency commonmode rejection. Mismatch common-mode input time constant (R1C1 either from stray capacitance mismatched values, causes high frequency common-mode signal converted differential signal. This degrades common-mode rejection. differential input capacitor, reduces bandwidth mitigates effects mismatch Make much larger than properly matched, also improve CMR.
INA121 G=1+
FIGURE Voltage Swing
INA121
+10V
Bridge
INA121
10C1
input allows large resistors small capacitors.
FIGURE Input Low-Pass Filter.
FIGURE Bridge Transducer Amplifier.
INA121
±18V Isolated Power
±15V
INA121
2R1C1
INA121
ISO124
NOTE: preserve good frequency CMR, make
Isolated Common
FIGURE High-Pass Input Filter.
FIGURE Galvanically Isolated Instrumentation Amplifier.
OPA277
INA121 0.1µF
50nF
INA121
OPA277
f-3dB 2R1C1 1.59Hz
Make where Load
FIGURE AC-Coupled Instrumentation Amplifier.
FIGURE Voltage Controlled Current Source.
Transducer
Null
INA121
FIGURE Capacitive Bridge Transducer Circuit.
INA121
VREF Channel MPC800 Channel INA121 ADS7816 Bits Serial
FIGURE Multiplexed-Input Data Acquisition System.
22.1k 22.1k
INA121
NOTE: Driving shield minimizes degradation unequally distributed capacitance input line. shield driven approximately below common-mode input voltage. OPA130
2(22.1k) effective
FIGURE Shield Driver Circuit.
5.6k 2.8k RG/2 2.8k 390k bias current allows with high electrode impedances. 390k OPA2131 OPA2131 NOTE: INA121's current-feedback topology, approximately 0.7V less than common-mode input voltage. This offset this guard potential satisfactory many guarding applications. INA121
FIGURE Amplifier With Right-Leg Drive.
INA121

INA121 FET-Input, Power INSTRUMENTATION AMPLIFIER FEATURES

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