TLV316-Q1 Datasheet, PDF (14/31 Pages) Texas Instruments – 10-MHz, Rail-to-Rail Input/Output, Low-Voltage, 1.8-V CMOS Operational Amplifiers

TLV316-Q1, TLV2316-Q1, TLV4316-Q1
SBOS845A – NOVEMBER 2016 – REVISED DECEMBER 2016
www.ti.com
7.3 Feature Description
7.3.1 Operating Voltage
The TLVx316-Q1 operational amplifiers are fully specified and ensured for operation from 1.8 V to 5.5 V. In
addition, many specifications apply from –40°C to +125°C. Parameters that vary significantly with operating
voltages or temperature are illustrated in the Typical Characteristics section.
7.3.2 Rail-to-Rail Input
The input common-mode voltage range of the TLVx316-Q1 extends 200 mV beyond the supply rails for supply
voltages greater than 2.5 V. 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 the Functional Block Diagram. The N-
channel pair is active for input voltages close to the positive rail, typically (V+) – 1.4 V to 200 mV above the
positive supply, whereas the P-channel pair is active for inputs from 200 mV below the negative supply to
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 Rail-to-Rail Output
Designed as a low-power, low-voltage operational amplifier, the TLVx316-Q1 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; see .
7.3.4 Common-Mode Rejection Ratio (CMRR)
CMRR for the TLVx316-Q1 is specified in two ways so the best match for a given application can be selected.
The Electrical Characteristics table provides 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 using one of the differential input pairs. 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 through the transition
region.
7.3.5 Capacitive Load and Stability
The TLVx316-Q1 is designed for applications where driving a capacitive load is required. As with all operational
amplifiers, there may be specific instances where the TLVx316-Q1 can become unstable. The particular
operational amplifier circuit configuration, layout, gain, and output loading are some of the factors to consider
when establishing whether or not an amplifier is stable in operation. An operational amplifier in the unity-gain (1
V/V) buffer configuration that drives a capacitive load exhibits a greater tendency to be unstable than an amplifier
operated at a higher noise gain. The capacitive load, in conjunction with the operational amplifier output
resistance, creates a pole within the feedback loop that degrades the phase margin. The degradation of the
phase margin increases when the capacitive loading increases. For a conservative best practice, designing for
25% overshoot (40° phase margin) provides improved stability over process variations. The equivalent series
resistance (ESR) of some very-large capacitors (C_L capacitors with a value greater than 1 μF) is sufficient to alter
the phase characteristics in the feedback loop such that the amplifier remains stable. Increasing the amplifier
closed-loop gain allows the amplifier to drive increasingly larger capacitance. This increased capability is evident
when observing the overshoot response of the amplifier at higher voltage gains, as shown in Figure 7 (G = –1
V/V).
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