LT1002ACN datasheet(10/16 Pages) LINER

10 / 16 page

LT1002

APPLICATIONS INFORMATION

Advantages of Matched Dual Op Amps In many applica-

tions the performance of a system depends on the match-

ing between two operational amplifiers rather than the

individual characteristics of the two op amps. Two or three

op amp instrumentation amplifiers, tracking voltage refer-

ences and low drift active filters are some of the circuits

requiring matching between two op amps.

The well-known triple op amp configuration illustrates

these concepts. Output offset is a function of the differ-

ence between the offsets of the two halves of the LT1002.

This error cancellation principle holds for a considerable

number of input referred parameters in addition to offset

voltage and its drift with temperature. Input bias current

will be the average of the two non-inverting input currents

(IB+). The difference between these two currents (IOS+) is

the offset current of the instrumentation amplifier. The

difference between the inverting input currents (IOS–) will

cause errors flowing through R1, R2, and R3. Common-

mode and power supply rejections will be dependent only

on the match between the two amplifiers (assuming

perfect resistor matching).

The concepts of common mode and power supply rejec-

tion ratio match (

∆CMRR and ∆PSRR) are best demon-

strated with a numerical example:

Assume CMRRA = +1.0µV/V or 120dB,

and CMRRB = +0.75µV/V or 122.5dB,

then

∆CMRR = 0.25µV/V or 132dB;

if CMRRB = – 0.75µV/V which is still 122.5dB,

then

∆CMRR = 1.75µV/V or 115dB.

Clearly, the LT1002, by specifying and guaranteeing all of

these matching parameters, can significantly improve the

performance of matching dependent circuits.

1002 TA07

10k

100

Ω

10k

100

Ω

INPUT

OUTPUT

–

Gain = 1000

–

1/2 LT1002

–

/2 LT1002

LT1037

–

INPUT +

10k

9.76k

2.1k

100pF

R10

100k

200

Ω

200

Ω

Three Op Amp Instrumentation Amplifier

Trim R8 for gain

Trim R9 for DC common mode rejection

Trim R10 for AC common mode rejection

Typical performance of the instrumentation amplifier:

Input offset voltage = 25

µV

Input bias current = 0.7nA

Input resistance = 200 G

Ω

Input offset current = 0.6nA

Input noise = 0.5

µV p-p

Power bandwidth (V0 = ±10V) = 80kHz

LT1002ACN Datasheet(PDF) 10 Page - Linear Technology

LT1002ACN Datasheet(HTML) 10 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Datasheet Download

Link URL