OPA1641-Q1 Datasheet, PDF (20/31 Pages) Texas Instruments – SoundPlus JFET-Input, Automotive-Grade, Audio Operational Amplifiers

OPA1641-Q1, OPA1642-Q1
SBOS791 – JUNE 2017
www.ti.com
If the supply is not capable of sinking the current, V_IN can begin sourcing current to the operational amplifier, and
then take over as the source of positive supply voltage. The danger in this case is that the voltage can rise to
levels that exceed the operational amplifier absolute maximum ratings.
Another common question involves what happens to the amplifier if an input signal is applied to the input when
the power supplies +V_S and –V_S are at 0 V. The amplifier behavior depends on the supply characteristic when at
0 V, or at a level below the input signal amplitude. If the supplies appear as high impedance, then the operational
amplifier supply current can be supplied by the input source through the current steering diodes. This state is not
a normal bias condition; the amplifier most likely does not operate normally. If the supplies are low impedance,
then the current through the steering diodes can become quite high. The current level depends on the ability of
the input source to deliver current and any resistance in the input path.
If there is an uncertainty about the ability of the supply to absorb this current, external Zener diodes can be
added to the supply pins, as shown in Figure 36. The Zener voltage must be selected so the diode does not turn
on during normal operation. However, the Zener voltage must be low enough so that the Zener diode conducts if
the supply pin begins to rise above the safe operating supply voltage level.
(2)
TVS
R_F
I_D
V_IN(1)
R_I
-In
(3)
R_S
+In
+V_S
+V
OPA1641-Q1
Op-Amp
Core
ESD Current-
Steering Diodes
Out
Edge-Triggered ESD
Absorption Circuit
R_L
-V
-V_S
(2)
TVS
Copyright © 2016, Texas Instruments Incorporated
(1) V_IN = +V_S + 500 mV.
(2) TVS: +V_S(max) > V_{TVSBR (Min)} > +V_S
(3) Suggested value is approximately 1 kΩ.
Figure 36. Equivalent Internal ESD Circuitry and the Relation to a Typical Circuit Application
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