Datasheet

AD8270
Rev. 0 | Page 14 of 20
INPUT VOLTAGE RANGE
The AD8270 has a true rail-to-rail input range for the majority
of applications. Because most AD8270 configurations divide down
the voltage before they reach the internal op amp, the op amp sees
only a fraction of the input voltage.
Figure 41 shows an example
of how the voltage division works in the difference amplifier
configuration.
06979-061
R4
R3
R1
R2
R2
R1 + R2
(V
+IN
)
R2
R1 + R2
(V
+IN
)
Figure 41. Voltage Division in the Difference Amplifier Configuration
The internal op amp voltage range may be relevant in the
following applications, and calculating the voltage at the
internal op amp is advised.
• Difference amplifier configurations using supply voltages
of less than ±4.5 V
• Difference amplifier configurations with a reference
voltage near the rail
• Single-ended amplifier configurations
For correct operation, the input voltages at the internal op amp
must stay within 1.5 V of either supply rail.
Voltages beyond the supply rails should not be applied to the
part. The part contains ESD diodes at the input pins, which
conduct if voltages beyond the rails are applied. Currents greater
than 5 mA can damage these diodes and the part. For a similar
part that can operate with voltages beyond the rails, see the
AD8273 data sheet.