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	LMP7721 - 3 Femtoampere Input Bias Current Precision Amplifier from the PowerWise® Family

Features Unless otherwise noted, typical values at TA = 25°C, VS = 5V. Input bias current (VCM = 1V) max @ 25°C ±20 fA max @ 85°C ±900 fA Offset voltage ±26 µV Offset voltage drift −1.5 μV/°C DC Open loop gain 120 dB DC CMRR 100 dB Input voltage noise (at f = 1 kHz) 6.5 nV/ √Hz THD 0.0007% Supply current 1.3 mA GBW 17 MHz Slew rate (falling edge) 12.76 V/μs Supply voltage 1.8V to 5.5V Operating temperature range −40°C to 125°C 8-Pin SOIC General Description The LMP7721 is the industry’s lowest guaranteed input bias current precision amplifier. More... Applications   • Photodiode amplifier • High impedance sensor amplifier • Ion chamber amplifier • Electrometer amplifier • pH electrode amplifier • Transimpedance amplifier

Typical Application click for larger image Parametric Table     expand Parametric Table    collapse Offset Voltage max, 25C 0.150 mV TcVos 1.5 uV/degC CMRR 100 dB PSRR 96 dB Avol 120 dB Voltage Noise 6.5 nV/√Hz Max Input Bias Current 0.00002 nA Gain Bandwidth 17 MHz Supply Current Per Channel 1.3 mA PowerWise Rating 2 76.5 uA/MHz Offset Voltage max, 25C 0.150 mV TcVos 1.5 uV/degC CMRR 100 dB PSRR 96 dB Avol 120 dB Voltage Noise 6.5 nV/√Hz Max Input Bias Current 0.00002 nA Gain Bandwidth 17 MHz Supply Current Per Channel 1.3 mA PowerWise Rating 2 76.5 uA/MHz Slew Rate 10.5 Volts/usec Channels 1 Channels Supply Min 1.8 Volt Supply Max 5.5 Volt Input OutputType Vcm to V-, R-R Out Output Current 22 mA Shut down No Special Features 3fA Guaranteed Temperature Min -40 deg C Temperature Max 125 deg C Function Op Amp PowerWise Yes View Using Catalog Typical Performance click for larger image

Additional Resources Application Notes (see below) Connection Diagram click for larger image

RoHS Compliance Information	Size in Kbytes	Date
LMP7721 3 Femtoampere Input Bias Current Precision Amplifier	602 Kbytes	14-Mar-08	View Online	Download	Receive via Email

Part Number

Package

Factory Lead Time

Models

Samples & Electronic Orders

Budgetary Pricing

Std Pack Size

Package Marking Format

Type

Pins

Spec.

MSL Rating

Peak Reflow

RoHS Report

CAD Symbols

Weeks

Qty

Qty

$US each

LMP7721MAE

SOIC NARROW

8

RoHS

N/A

Full production

LMP7721.MOD

CALL

reel of N/A

NSZXTT LMP77 21MA

N/A

N/A

LMP7721MA

SOIC NARROW

8

NOPB

1

260

RoHS

N/A

Full production

LMP7721.MOD

1K+

$4.95

rail of 95

NSZXTT LMP77 21MA

16 weeks

2000

LMP7721MAX

SOIC NARROW

8

NOPB

1

260

RoHS

N/A

Full production

LMP7721.MOD

1K+

$4.95

reel of 2500

NSZXTT LMP77 21MA

16 weeks

N/A

General Description

The LMP7721 is the industry’s lowest guaranteed input bias current precision amplifier. The ultra low input bias current is 3 fA, with a guaranteed limit of ±20 fA at 25°C and ±900 fA at 85°C. This is achieved with the latest patent pending technology of input bias current cancellation amplifier circuitry. This technology also maintains the ultra low input bias current over the entire input common mode voltage range of the amplifier.

Other outstanding features, such as low voltage noise (6.5 nV/ ), low DC offset voltage (±150 µV maximum at 25°C) and low offset voltage temperature coefficient (−1.5 µV/°C), improve system sensitivity and accuracy in high precision applications. With a supply voltage range of 1.8V to 5.5V, the LMP7721 is the ideal choice for battery operated portable applications. The LMP7721 is part of the LMP precision amplifier family.

As part of National’s PowerWise products, the LMP7721 provides the remarkably wide gain bandwidth product (GBW) of 17 MHz while consuming only 1.3 mA of current. This wide GBW along with the high open loop gain of 120 dB enables accurate signal conditioning. With these specifications, the LMP7721 has the performance to excel in a wide variety of applications such as electrochemical cell amplifiers and sensor interface circuits.

The LMP7721 is offered in an 8-pin SOIC package with a special pinout that isolates the amplifier’s input from the power supply and output pins. With proper board layout techniques, the unique pinout of the LMP7721 will prevent PCB leakage current from reaching the input pins. Thus system error will be further reduced.

Application Notes

Title	Size in Kbytes	Date
AN-1796: Application Note 1796 LMP7721 Evaluation Board	136 Kbytes	5-Mar-08	View Online	Download	Receive via Email
AN-1798: Application Note 1798 Designing with Electro-Chemical Sensors	140 Kbytes	9-Apr-08	View Online	Download	Receive via Email

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