OPA2314-Q1 Datasheet, PDF (14/28 Pages) Texas Instruments – 3-MHz, Low-Power, Low-Noise, RRIO, 1.8-V CMOS Operational Amplifier

OPA2314-Q1
SLOS896A – DECEMBER 2014 – REVISED JANUARY 2015
www.ti.com
Feature Description (continued)
7.3.3 Input and ESD Protection
The OPA2314-Q1 device 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 table. Figure 33 shows how a
series input resistor can be added to the driven input to limit the input current. The added resistor contributes
thermal noise at the amplifier input and the 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 33. Input Current Protection
7.3.4 Common-Mode Rejection Ratio (CMRR)
CMRR for the OPA2314-Q1 device is specified in several ways so the best match for a given application may be
used; see the Electrical Characteristics table. First, the CMRR of the device in the common-mode range below
the transition region [V_CM < (V+) – 1.3 V] is given. This specification is the best indicator of the capability of the
device when the application requires use of one of the differential input pairs. Second, the CMRR over the entire
common-mode range is specified at (V_CM = –0.2 V to 5.7 V). This last value includes the variations seen through
the transition region (see Figure 7).
7.3.5 EMI Susceptibility and Input Filtering
Op-amps vary with regard to the susceptibility of the device to electromagnetic interference (EMI). If conducted
EMI enters the op-amp, the dc offset observed at the amplifier output may shift from the nominal value while EMI
is present. This shift is a result of signal rectification associated with the internal semiconductor junctions. While
all op-amp pin functions can be affected by EMI, the signal input pins are likely to be the most susceptible. The
OPA2314-Q1 device incorporates an internal input low-pass filter that reduces the amplifiers response to EMI.
Both common-mode and differential mode filtering are provided by this filter. The filter is designed for a cutoff
frequency of approximately 80 MHz (–3 dB), with a roll-off of 20 dB per decade.
Texas Instruments has developed the ability to accurately measure and quantify the immunity of an operational
amplifier over a broad frequency spectrum extending from 10 MHz to 6 GHz. The EMI rejection ratio (EMIRR)
metric allows op-amps to be directly compared by the EMI immunity. Figure 32 shows the results of this testing
on the OPA2314-Q1 device. Detailed information can also be found in the application report, EMI Rejection Ratio
of Operational Amplifiers (SBOA128), available for download from www.ti.com.
7.3.6 Rail-to-Rail Output
Designed as a micro-power, low-noise operational amplifier, the OPA2314-Q1 device delivers a robust output
drive capability. A class AB output stage with common-source transistors is used to achieve full rail-to-rail output
swing capability. For resistive loads up to 10 kΩ, the output swings typically to within 5 mV of either supply rail
regardless of the power-supply voltage applied. Different load conditions change the ability of the amplifier to
swing close to the rails; refer to the graph, Output Voltage Swing vs Output Current.
7.4 Device Functional Modes
The OPA2314-Q1 device is powered on when the supply is connected. The device can be operated as a single-
supply operational amplifier or a dual-supply amplifier, depending on the application.
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