OPA2316 Datasheet, PDF (17/46 Pages) Texas Instruments – OPAx316 10-MHz, Low-Power, Low-Noise, RRIO, 1.8-V CMOS Operational Amplifier

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OPA316, OPA2316, OPA2316S, OPA4316
SBOS703D – APRIL 2014 – REVISED DECEMBER 2014
Feature Description (continued)
approximately (V+) – 1.4 V. There is a small transition region, typically (V+) – 1.2 V to (V+) – 1 V, in which both
pairs are on. This 200-mV transition region can vary up to 200 mV with process variation. Thus, the transition
region (both stages on) can range from (V+) – 1.4 V to (V+) – 1.2 V on the low end, up to (V+) – 1 V to (V+) –
0.8 V on the high end. Within this transition region, PSRR, CMRR, offset voltage, offset drift, and THD can be
degraded compared to device operation outside this region.
7.3.3 Input and ESD Protection
The OPA316 family incorporates internal 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 37 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
its value must be kept to a minimum in noise-sensitive applications.
I_OVERLOAD
10-mA max
V_IN
5 kW
V+
Device
V_OUT
Figure 37. Input Current Protection
7.3.4 Common-Mode Rejection Ratio (CMRR)
CMRR for the OPA316 is specified in several ways so the user can select the best match for a given application
(see the Electrical Characteristics). First, the data sheet gives the CMRR of the device in the common-mode
range below the transition region [V_CM < (V+) – 1.4 V]. This specification is the best indicator of device capability
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 for V_S = 5.5 V. This last value includes the variations
seen (TBD cannot use "seen") through the transition region (see Figure 4).
7.3.5 EMI Susceptibility and Input Filtering
Operational amplifiers vary with regard to the susceptibility of the device to electromagnetic interference (EMI). If
conducted EMI enters the operational amplifier, the dc offset observed at the amplifier output can shift from its
nominal value when EMI is present. This shift is a result of signal rectification associated with the internal
semiconductor junctions. Although all operational amplifier pin functions can be affected by EMI, the signal input
pins are likely to be the most susceptible. The OPA316 operational amplifier family incorporates an internal input
low-pass filter that reduces the amplifier response to EMI. This filter provides both common-mode and
differential-mode filtering. The filter is designed for a cutoff frequency of approximately 80 MHz (–3 dB), with a
roll-off of 20 dB per decade.
TI 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 operational
amplifiers to be directly compared by the EMI immunity. Figure 35 illustrates the results of this testing on the
OPA316. 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 low-power, low-noise operational amplifier, the OPA316 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 of 10 kΩ, the output swings typically to within 30 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 typical characteristic graph Output Voltage Swing vs Output Current (Figure 11).
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Product Folder Links: OPA316 OPA2316 OPA2316S OPA4316