Datasheet

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INA121

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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

INA121

FEATURES

● LOW BIAS CURRENT: ±4pA

● LOW QUIESCENT CURRENT:

±450µA

● LOW INPUT OFFSET VOLTAGE:

±200µV

● LOW INPUT OFFSET DRIFT:

±2µV/°C

● LOW INPUT NOISE:

20nV/√Hz at f = 1kHz (G =100)

● HIGH CMR: 106dB

● WIDE SUPPLY RANGE:

±2.25V to ±18V

● LOW NONLINEARITY ERROR: 0.001% max

● INPUT PROTECTION TO

±40V

● 8-PIN DIP AND SO-8 SURFACE MOUNT

FET-Input, Low Power

INSTRUMENTATION AMPLIFIER

DESCRIPTION

The INA121 is a FET-input, low power instrumenta-

tion amplifier offering excellent accuracy. Its versatile

three-op amp design and very small size make it ideal

for a variety of general purpose applications. Low bias

current (±4pA) allows use with high impedance

sources.

Gain can be set from 1V to 10,000V/V with a single

external resistor. Internal input protection can with-

stand up to ±40V without damage.

The INA121 is laser-trimmed for very low offset

voltage (±200µV), low offset drift (±2µV/°C), and

high common-mode rejection (106dB at G = 100). It

operates on power supplies as low as ±2.25V (+4.5V),

allowing use in battery operated and single 5V sys-

tems. Quiescent current is only 450µA.

Package options include 8-pin plastic DIP and SO-8

surface mount. All are specified for the –40°C to

+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

40kΩ40kΩ

V+

V–

INA121

Ref

G = 1 +

50kΩ

–

Over-Voltage

Protection

25kΩ

Over-Voltage

Protection

SBOS078

Summary of content (17 pages)

PAGE 1
® INA INA121 121 INA 121 FET-Input, Low Power INSTRUMENTATION AMPLIFIER FEATURES DESCRIPTION ● LOW BIAS CURRENT: ±4pA ● LOW QUIESCENT CURRENT: ±450µA The INA121 is a FET-input, low power instrumentation amplifier offering excellent accuracy. Its versatile three-op amp design and very small size make it ideal for a variety of general purpose applications. Low bias current (±4pA) allows use with high impedance sources.
PAGE 2
SPECIFICATIONS: VS = ±15V At TA = +25°C, VS = ±15V, RL = 10kΩ, and IA reference = 0V, unless otherwise noted. INA121P, U PARAMETER CONDITIONS INPUT Offset Voltage, RTI vs Temperature vs Power Supply Long-Term Stability Impedance, Differential Common-Mode Input Voltage Range Safe Input Voltage Common-Mode Rejection VS = ±2.25V to ±18V VO = 0V VCM = –12.5V to 13.
PAGE 3
ELECTROSTATIC DISCHARGE SENSITIVITY PIN CONFIGURATION Top View 8-Pin DIP and SO-8 This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. Top View RG 1 8 RG V–IN 2 7 V+ + IN 3 6 VO V– 4 5 Ref V ESD damage can range from subtle performance degradation to complete device failure.
PAGE 4
TYPICAL PERFORMANCE CURVES At TA = +25°C, VS = ±15V, unless otherwise noted.
PAGE 5
TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, VS = ±15V, unless otherwise noted. INPUT BIAS CURRENT vs COMMON-MODE INPUT VOLTAGE 10k 1m 1k 100µ Input Bias Current (A) Bias Current (pA) INPUT BIAS CURRENT vs TEMPERATURE 100 10 IB 1 IOS 0.1 0.01 –75 10µ 10p 1p –10µ –100µ –50 –25 0 25 50 75 100 125 Temperature (°C) –1m –20 –15 –10 –5 0 5 10 15 20 Common-Mode Voltage (V) SETTLING TIME vs GAIN INPUT OVER-VOLTAGE V/I CHARACTERISTICS 1000 1 0.
PAGE 6
TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, VS = ±15V, unless otherwise noted. OUTPUT VOLTAGE SWING vs OUTPUT CURRENT MAXIMUM OUTPUT VOLTAGE vs FREQUENCY V+ +85°C (V+) –0.6 +25°C (V+) –0.9 –40°C, –55°C (V+) –1.2 +125°C (V+) –1.5 (V–) +1.5 +125°C (V–) +1.2 +85°C (V–) +0.9 +25°C (V–) +0.6 –40°C, –55°C (V–) +0.
PAGE 7
TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, VS = ±15V, unless otherwise noted.
PAGE 8
APPLICATION INFORMATION The 50kΩ term in Equation 1 comes from the sum of the two internal feedback resistors of A1 and A2. These on-chip metal film resistors are laser trimmed to accurate absolute values. The accuracy and temperature coefficient of these resistors are included in the gain accuracy and drift specifications of the INA121. Figure 1 shows the basic connections required for operation of the INA121.
PAGE 9
The INA121 provides excellent rejection of high frequency common-mode signals. The typical performance curve, “Common-Mode Rejection vs Frequency” shows this behavior. If the inputs are not properly balanced, however, common-mode signals can be converted to differential sig– + nals. Run the VIN and VIN connections directly adjacent each other, from the source signal all the way to the input pins. If possible use a ground plane under both input traces.
PAGE 10
A combination of common-mode and differential input voltage can cause the output of A1 or A2 to saturate. Figure 4 shows the output voltage swing of A1 and A2 expressed in terms of a common-mode and differential input voltages. For applications where input common-mode range must be maximized, limit the output voltage swing by connecting the INA121 in a lower gain (see performance curve “Input Common-Mode Voltage Range vs Output Voltage”).
PAGE 11
±6V to ±18V Isolated Power C1 V+ V– ±15V RG C2 VO INA121 Ref – VIN R1 R2 INA121 1 2πR1C1 fc = + VO ISO124 Ref VIN NOTE: To preserve good low frequency CMR, make R1 = R2 and C1 = C2. Isolated Common FIGURE 7. High-Pass Input Filter. FIGURE 8. Galvanically Isolated Instrumentation Amplifier. VIN OPA277 – VIN + RG INA121 Ref C1 50nF VO C1 0.1µF R1 1MΩ R1 10kΩ INA121 1 f–3dB = 2πR1C1 OPA277 RG R2 Ref IL = = 1.59Hz Make G ≤ 10 where G = 1 + 50k RG FIGURE 9.
PAGE 12
+5V VREF Channel 1 VIN + – +In MPC800 MUX Channel 8 VIN 12 Bits Out Serial ADS7816 INA121 RG –In + – Ref FIGURE 12. Multiplexed-Input Data Acquisition System. – VIN 22.1kΩ 22.1kΩ + VIN 511Ω VO INA121 Ref 100Ω NOTE: Driving the shield minimizes CMR degradation due to unequally distributed capacitance on the input line. The shield is driven at approximately 1V below the common-mode input voltage. OPA130 For G = 100 RG = 511Ω // 2(22.1kΩ) effective RG = 505Ω FIGURE 13.
PAGE 13
PACKAGE OPTION ADDENDUM www.ti.
PAGE 14
PACKAGE OPTION ADDENDUM www.ti.com 16-Feb-2009 In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
PAGE 15
PACKAGE MATERIALS INFORMATION www.ti.com 11-Mar-2008 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel Diameter Width (mm) W1 (mm) A0 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant INA121U/2K5 SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.0 Q1 INA121UA/2K5 SOIC D 8 2500 330.0 12.4 6.4 5.2 2.1 8.0 12.
PAGE 16
PACKAGE MATERIALS INFORMATION www.ti.com 11-Mar-2008 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) INA121U/2K5 SOIC D 8 2500 346.0 346.0 29.0 INA121UA/2K5 SOIC D 8 2500 346.0 346.0 29.
PAGE 17
IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.