LT6011/LT6012

10

sn60112 60112fas

Small-Signal Transient Response

Large-Signal Transient Response

Rail-to-Rail Output Swing

20mV/DIV

2

µs/DIV

6011 G28

2V/DIV

50

µs/DIV

6011 G29

1V/DIV

100

µs/DIV

6011 G30

TYPICAL PERFOR A CE CHARACTERISTICS

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Preserving Input Precision

Preserving the input accuracy of the LT6011/LT6012 re-

quires that the applications circuit and PC board layout do

not introduce errors comparable to or greater than the 25

µV

typical offset of the amplifiers. Temperature differentials

across the input connections can generate thermocouple

voltages of 10’s of microvolts so the connections to the input

leads should be short, close together and away from heat

dissipating components. Air currents across the board can

also generate temperature differentials.

The extremely low input bias currents (20pA typical) allow

high accuracy to be maintained with high impedance

sources and feedback resistors. The LT6011/LT6012 low

input bias currents are obtained by a cancellation circuit

in each input lead; instead keep the resistance at either input

as low as possible for maximum accuracy.

Leakage currents on the PC board can be higher than the

input bias current. For example, 10G

Ωofleakagebetween

a 15V supply lead and an input lead will generate 1.5nA!

Surround the input leads with a guard ring driven to the

same potential as the input common mode to avoid exces-

sive leakage in high impedance applications.

Input Protection

The LT6011/LT6012 feature on-chip back-to-back diodes

between the input devices, along with 500

Ω resistors in

series with either input. This internal protection limits the

input current to approximately 10mA (the maximum al-

lowed) for a 10V differential input voltage. Use additional

external series resistors to limit the input current to 10mA

in applications where differential inputs of more than 10V

are expected. For example, a 1k resistor in series with each

input provides protection against 30V differential voltage.

Input Common Mode Range

The LT6011/LT6012 output is able to swing close to each

power supply rail (rail-to-rail out), but the input stage is

ing this common mode range will cause the gain to drop

to zero, however, no phase reversal will occur.

Total Input Noise

The LT6011/LT6012 amplifier contributes negligible noise

to the system when driven by sensors (sources) with

impedance between 20k

Ω and 1MΩ. Throughout this

of the source. If the source impedance is less than 20k

Ω,

the input voltage noise of the amplifier starts to contribute

with a minimum noise of 14nV/

√Hzforverylowsourceim-

pedance. If the source impedance is more than 1M

Ω, the

input current noise of the amplifier, multiplied by this high

impedance, starts to contribute and eventually dominate.

Total input noise spectral density can be calculated as:

v

e

kTR

i R

n TOTAL

n

S

n S

()

()

=+

+

2

2

4

APPLICATIO S I FOR ATIO

5V