LT1468CS8-2(RevB) View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
LT1468CS8-2 Datasheet PDF : 14 Pages
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LT1468-2
applications information
Input Considerations
Each input of the LT1468-2 is protected with a 100Ω
series resistor and back-to-back diodes across the bases
of the input devices. If the inputs can be pulled apart, the
input current should be limited to less than 10mA with
an external series resistor. Each input also has two ESD
clamp diodes—one to each supply. If an input is driven
above the supply, limit the current with an external resistor
to less than 10mA.
The LT1468-2 employs bias current cancellation at the
inputs. The inverting input current is trimmed at zero
common mode voltage to minimize errors in inverting
applications such as I-to-V converters. The noninverting
input current is not trimmed and has a wider variation
and therefore a larger maximum value. As the input offset
current can be greater than either input current, the use
of balanced source resistance is NOT recommended as it
actually degrades DC accuracy and also increases noise.
The input bias currents vary with common mode voltage
as shown in the Typical Performance Characteristics. The
cancellation circuitry was not designed to track this com-
mon mode voltage because the settling time would have
been adversely affected.
The LT1468 inputs can be driven to the negative supply
and to within 0.5V of the positive supply without phase
reversal. As the input moves closer than 0.5V to the posi-
tive supply, the output reverses phase.
Total Input Noise
The curve of Total Noise vs Unmatched Source Resistance
in the Typical Performance Characteristics shows that
with source resistance below 1k, the voltage noise of the
amplifier dominates. In the 1k to 20k region the increase in
noise is due to the source resistance. Above 20k the input
current noise component is larger than the resistor noise.
Input Stage Protection
R1
100Ω Q1
+IN
R2
Q2 100Ω
–IN
14682 AI03
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