LMV931-N-Q1 Datasheet, PDF (17/40 Pages) Texas Instruments – LMV93x-N/-N-Q1 Single, Dual, Quad 1.8-V, RRIO Operational Amplifiers

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LMV931-N, LMV931-N-Q1
LMV932-N, LMV932-N-Q1, LMV934-N, LMV934-N-Q1
SNOS993O – NOVEMBER 2001 – REVISED DECEMBER 2014
Device Functional Modes (continued)
This V_OS crossover point can create problems for both DC− and AC-coupled signals if proper care is not taken.
Large input signals that include the V_OS crossover point will cause distortion in the output signal. One way to
avoid such distortion is to keep the signal away from the crossover. For example, in a unity gain buffer
configuration with V_S = 5 V, a 5-V peak-to-peak signal will contain input-crossover distortion while a 3-V peak-to-
peak signal centered at 1.5 V will not contain input-crossover distortion as it avoids the crossover point. Another
way to avoid large signal distortion is to use a gain of −1 circuit which avoids any voltage excursions at the input
terminals of the amplifier. In that circuit, the common-mode DC voltage can be set at a level away from the V_OS
cross-over point. For small signals, this transition in V_OS shows up as a V_CM dependent spurious signal in series
with the input signal and can effectively degrade small signal parameters such as gain and common-mode
rejection ratio. To resolve this problem, the small signal should be placed such that it avoids the V_OS crossover
point. In addition to the rail-to-rail performance, the output stage can provide enough output current to drive 600-
Ω loads. Because of the high-current capability, take care not to exceed the 150°C maximum junction
temperature specification.
7.4.2 Input Bias Current Consideration
The LMV93x-N family has a complementary bipolar input stage. The typical input bias current (I_B) is 15 nA. The
input bias current can develop a significant offset voltage. This offset is primarily due to I_B flowing through the
negative feedback resistor, R_F. For example, if I_B is 50 nA and R_F is 100 kΩ, then an offset voltage of 5 mV will
develop (V_OS = I_B x R_F). Using a compensation resistor (R_C), as shown in Figure 29, cancels this effect. But the
input offset current (I_OS) will still contribute to an offset voltage in the same manner.
Figure 29. Canceling the Offset Voltage due to Input Bias Current
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