LF355 datasheet(22/32 Pages) TI

22 / 32 page

LF155, LF156, LF355, LF356, LF357

SNOSBH0C – MAY 2000 – REVISED MARCH 2013

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Figure 55. Fast Sample and Hold

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Both amplifiers (A1, A2) have feedback loops individually closed with stable responses (overshoot negligible)

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Acquisition time TA, estimated by:

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LF156 develops full Sr output capability for VIN ≥ 1V

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Addition of SW2 improves accuracy by putting the voltage drop across SW1 inside the feedback loop

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Overall accuracy of system determined by the accuracy of both amplifiers, A1 and A2

Figure 56. High Accuracy Sample and Hold

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By closing the loop through A2, the VOUT accuracy will be determined uniquely by A1.

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No VOS adjust required for A2.

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TA can be estimated by same considerations as previously but, because of the added

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propagation delay in the feedback loop (A2) the overshoot is not negligible.

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Overall system slower than fast sample and hold

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R1, CC: additional compensation

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Use LF156 for

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Fast settling time

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Low VOS

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LF355 Datasheet(PDF) 22 Page - Texas Instruments