OPA314_15 Datasheet, PDF (17/45 Pages) Texas Instruments – OPAx314 3-MHz, Low-Power, Low-Noise, RRIO, 1.8-V CMOS Operational Amplifier

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OPA314, OPA2314, OPA4314
SBOS563G – MAY 2011 – REVISED JUNE 2015
Feature Description (continued)
7.3.2 Rail-to-Rail Input
The input common-mode voltage range of the OPA314 series extends 200 mV beyond the supply rails. This
performance is achieved with a complementary input stage: an N-channel input differential pair in parallel with a
P-channel differential pair, as shown in Figure 33. The N-channel pair is active for input voltages close to the
positive rail, typically (V+) – 1.3 V to 200 mV above the positive supply, while the P-channel pair is on for inputs
from 200 mV below the negative supply to approximately (V+) – 1.3 V. There is a small transition region, typically
(V+) – 1.4 V to (V+) – 1.2 V, in which both pairs are on. This 200-mV transition region can vary up to 300 mV
with process variation. Thus, the transition region (both stages on) can range from (V+) – 1.7 V to (V+) – 1.5 V
on the low end, up to (V+) – 1.1 V to (V+) – 0.9 V on the high end. Within this transition region, PSRR, CMRR,
offset voltage, offset drift, and THD may be degraded compared to device operation outside this region.
V+
Reference
Current
V_IN+
V_IN-
V_BIAS1
Class AB
Control
V_O
Circuitry
V_BIAS2
V-
(Ground)
Figure 33. Simplified Schematic
7.3.3 Input and ESD Protection
The OPA314 family incorporates internal electrostatic discharge (ESD) protection circuits on all pins. In the case
of input and output pins, this protection primarily consists of current-steering diodes connected between the input
and power-supply pins. These ESD protection diodes also provide in-circuit, input overdrive protection, as long
as the current is limited to 10 mA as stated in the Absolute Maximum Ratings . Figure 34 shows how a series
input resistor may be added to the driven input to limit the input current. The added resistor contributes thermal
noise at the amplifier input and its value should be kept to a minimum in noise-sensitive applications.
I_OVERLOAD
10-mA max
V_IN
5 kW
V+
Device
V_OUT
Figure 34. Input Current Protection
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