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 resis-

tor. 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 iso-

lation 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 sup-

plies

for

the

integrated

circuit

never

become

reversed — even under transient conditions. With reverse

voltages greater than 1V, the IC will conduct excessive cur-

rent, 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. Rever-

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 k

Ω, 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 over-

compensate the amplifier with a larger compensation capaci-

tor. 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 by-

passing, 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 by-

pass the supply leads of each amplifier with low inductance

capacitors because of the higher frequencies involved.

Standard Compensation and

Offset Balancing Circuit

DS007752-29

Fast Voltage Follower

DS007752-31

Power Bandwidth: 15 kHz

Slew Rate: 1V/µs

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