Datasheet

LMC662

SNOSC51C –APRIL 1998–REVISED MARCH 2013

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However, if the feedback pole is less than approximately 6 to 10 times the “ideal” −3 dB frequency, a feedback

capacitor, C

, should be connected between the output and the inverting input of the op amp. This condition can

also be stated in terms of the amplifier's low-frequency noise gain: To maintain stability, a feedback capacitor will

probably be needed if:

(2)

where:

(3)

is the amplifier's low-frequency noise gain and GBW is the amplifier's gain bandwidth product. An amplifier's low-

frequency noise gain is represented by the formula:

(4)

regardless of whether the amplifier is being used in an inverting or non-inverting mode. Note that a feedback

capacitor is more likely to be needed when the noise gain is low and/or the feedback resistor is large.

If the above condition is met (indicating a feedback capacitor will probably be needed), and the noise gain is

large enough that:

(5)

the following value of feedback capacitor is recommended:

(6)

(7)

the feedback capacitor should be:

(8)

Note that these capacitor values are usually significantly smaller than those given by the older, more

conservative formula:

(9)

consists of the amplifier's input capacitance plus any stray capacitance from the circuit board and socket. C

compensates for the pole caused by C

and the feedback resistor.

Figure 16. General Operational Amplifier Circuit

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