LMP7721

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SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014

Device Functional Modes (continued)

(7)

the feedback capacitor should be:

(8)

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

formula:

(9)

NOTE

CS consists of the amplifier’s input capacitance plus any stray capacitance from the circuit

board. CF compensates for the pole caused by CS and the feedback resistors.

Using the smaller capacitors will give much higher bandwidth with little degradation of transient response. It may

be necessary in any of the above cases to use a somewhat larger feedback capacitor to allow for unexpected

stray capacitance, or to tolerate additional phase shifts in the loop, or excessive capacitive load, or to decrease

the noise or bandwidth, or simply because the particular circuit implementation needs more feedback

capacitance to be sufficiently stable. For example, a printed circuit board’s stray capacitance may be larger or

smaller than the breadboard’s, so the actual optimum value for CF may be different from the one estimated using

the breadboard. In most cases, the values of CF should be checked on the actual circuit, starting with the

computed value.

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