Datasheet

LM101A-N, LM201A-N, LM301A-N
SNOSBS0D –SEPTEMBER 1999–REVISED MARCH 2013 www.ti.com
Although the LM101A is designed for trouble free operation, experience has indicated that it is wise to observe
certain precautions given below to protect the devices from abnormal operating conditions. It might be pointed
out that the advice given here is applicable to practically any IC op amp, although the exact reason why may
differ with different devices.
When driving either input from a low-impedance source, a limiting resistor should be placed in series with the
input lead to limit the peak instantaneous output current of the source to something less than 100 mA. This is
especially important when the inputs go outside a piece of equipment where they could accidentally be
connected to high voltage sources. Large capacitors on the input (greater than 0.1 μF) should be treated as a
low source impedance and isolated with a resistor. Low impedance sources do not cause a problem unless their
output voltage exceeds the supply voltage. However, the supplies go to zero when they are turned off, so the
isolation is usually needed.
The output circuitry is protected against damage from shorts to ground. However, when the amplifier output is
connected to a test point, it should be isolated by a limiting resistor, as test points frequently get shorted to bad
places. Further, when the amplifer drives a load external to the equipment, it is also advisable to use some sort
of limiting resistance to preclude mishaps.
Precautions should be taken to insure that the power supplies for the integrated circuit never become
reversed—even under transient conditions. With reverse voltages greater than 1V, the IC will conduct excessive
current, fusing internal aluminum interconnects. If there is a possibility of this happening, clamp diodes with a
high peak current rating should be installed on the supply lines. Reversal of the voltage between V
+
and V
−
will
always cause a problem, although reversals with respect to ground may also give difficulties in many circuits.
The minimum values given for the frequency compensation capacitor are stable only for source resistances less
than 10 kΩ, stray capacitances on the summing junction less than 5 pF and capacitive loads smaller than 100
pF. If any of these conditions are not met, it becomes necessary to overcompensate the amplifier with a larger
compensation capacitor. Alternately, lead capacitors can be used in the feedback network to negate the effect of
stray capacitance and large feedback resistors or an RC network can be added to isolate capacitive loads.
Although the LM101A is relatively unaffected by supply bypassing, this cannot be ignored altogether. Generally it
is necessary to bypass the supplies to ground at least once on every circuit card, and more bypass points may
be required if more than five amplifiers are used. When feed-forward compensation is employed, however, it is
advisable to bypass the supply leads of each amplifier with low inductance capacitors because of the higher
frequencies involved.
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Product Folder Links: LM101A-N LM201A-N LM301A-N