AD515AK AD [Analog Devices], AD515AK Datasheet

AD515AK

Manufacturer Part Number

AD515AK

Description

Monolithic Precision, Low Power FET-Input Electrometer Op Amp

Manufacturer

AD [Analog Devices]

Datasheet

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PRODUCT DESCRIPTION

The AD515A is a monolithic FET-input operational amplifier

with a guaranteed maximum input bias current of 75 fA

(AD515AL). The AD515A is a monolithic successor to the

industry standard AD515 electrometer, and will replace the

AD515 in most applications. The AD515A also delivers laser-

trimmed offset voltage, low drift, low noise and low power, a

combination of features not previously available in ultralow bias

current circuits. All devices are internally compensated, protected

against latch-up and are short circuit protected.

The AD515A’s combination of low input bias current, low

offset voltage and low drift optimizes it for a wide variety of

electrometer and very high impedance buffer applications

including photocurrent detection, vacuum ion-gage measure-

ment, long-term precision integration and low drift sample/hold

applications. This amplifier is also an excellent choice for all forms

of biomedical instrumentation such as pH/pIon sensitive elec-

trodes, very low current oxygen sensors, and high impedance

biological microprobes. In addition, the low cost and pin

compatibility of the AD515A with standard FET op amps will

allow designers to upgrade the performance of present systems

at little or no additional cost. The 10

impedance ensures that the input bias current is essentially

independent of common-mode voltage.

As with previous electrometer amplifier designs from Analog

Devices, the case is brought out to its own connection (Pin 8)

so it can be independently connected to a point at the same

potential as the input, thus minimizing stray leakage to the case.

This feature will also shield the input circuitry from external

noise and supply transients.

The AD515A is available in three versions of bias current and

offset voltage, the “J”, “K” and “L”; all are specified for rated

performance from 0 C to +70 C and supplied in a hermetically

sealed TO-99 package.

REV. A

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

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

FEATURES

Ultralow Bias Current: 75 fA max (AD515AL)

Ultralow Bias Current:

Low Power: 1.5 mA max Quiescent Current

Low Power:

Low Offset Voltage: 1.0 mV max (AD515AK & L)

Low Drift: 15 V/ C max (AD515AK)

Low Noise: 4 V p-p, 0.1 Hz to 10 Hz

(0.6 mA typ)

150 fA max (AD515AK)

300 fA max (AD515AJ)

common-mode input

Monolithic Precision, Low Power

PRODUCT HIGHLIGHTS

1. The AD515A provides subpicoampere bias currents in an

2. The input offset voltage on all grades is laser trimmed, typically

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700

Fax: 617/326-8703

3. The low quiescent current drain of 0.6 mA typical and

4. The combination of low input noise voltage and very low

FET-Input Electrometer Op Amp

integrated circuit amplifier.

• The ultralow input bias currents are specified as the maxi-

• By using 5 V supplies, input bias current can typically be

less than 500 V.

• The offset voltage drift is 15 V/ C maximum on the

• If additional pulling is desired, the amount required will

1.5 mA maximum, keeps self-heating effects to a minimum

and renders the AD515A suitable for a wide range of remote

probe applications.

input noise current is such that for source impedances from

dominate the noise characteristic.

mum measured at either input with the device fully warmed

up on 15 V supplies at +25 C ambient with no heat sink.

This parameter is 100% tested.

brought below 50 fA.

K grade.

have a minimal effect on offset drift (approximately 3 V/ C

per mV).

to 10

, the Johnson noise of the source will easily

PIN CONFIGURATION

World Wide Web Site: http://www.analog.com

AD515A

Related parts for AD515AK

AD515AK Summary of contents

Page 1

... Ultralow Bias Current: 300 fA max (AD515AJ) Low Power: 1.5 mA max Quiescent Current Low Power: (0.6 mA typ) Low Offset Voltage: 1.0 mV max (AD515AK & L) Low Drift max (AD515AK) Low Noise p-p, 0 PRODUCT DESCRIPTION The AD515A is a monolithic FET-input operational amplifier with a guaranteed maximum input bias current (AD515AL) ...

Page 2

... – +150 C AD515AJH AD515AKH possible for the input voltage to exceed the supply voltage, a series protection resistor should be added to limit input current to 0.1 mA. . The input devices can handle overload currents of 0.1 mA indefinitely without OS damage. See next page. ...

Page 3

LAYOUT AND CONNECTIONS CONSIDERATIONS The design of very high impedance measurement systems in- troduces a new level of problems associated with the reduction of leakage paths and noise pickup primary consideration in high impedance system designs is to ...

Page 4

AD515A COAXIAL CABLE AND CAPACITANCE EFFECTS not possible to attach the AD515A virtually on top of the signal source, considerable care should be exercised in designing the connecting lines carrying the high impedance signal. Shielded coaxial cable ...

Page 5

ELECTROMETER APPLICATION NOTES The AD515A offers subpicoampere input bias currents available in an integrated circuit package. This design will open up many new application opportunities for measurements from very high impedance and very low current sources. Performing accurate measurements of ...

Page 6

AD515A the total noise by about 40%. Noise currents driving the resistors also add, but in the AD515A are significant only above 10 Figure 11. Very High Impedance Instrumentation Amplifier Figure 12. Low Drift Integrator and Low Leakage Guarded Reset ...

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