Texas Instruments LFN Series Sample & Hold Amplifiers are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for Texas. lf Sample & Hold Amplifiers are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for lf Sample & Hold Amplifiers. Understand the working of LF IC (sample-and-hold circuit). • Describe the concept of sampling a time varying signal. • Obtain the sampled and hold otuput.

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The circuit is basically two unity-gain buffers, with a hold capacitor between them, and a switch to disconnect the input. For the LF, this is about 0.

For the LF, it is lg398. Record the time at the start, and at every even volt as the output voltage droops. Buffer a slow signal with an LS When the gate is connected to -V, the output will freeze, and you will note that it droops slowly but steadily. The similarity to our test circuit is obvious. Times from the hold command are measured from the 1. Lf3998 more practical discrete sample-and-hold circuit is given in Signal Switching. The control logic input is applied to a differential amplifier to allow interfacing with various logic families.


For a hold capacitor of 0. The acquisition time is the time for lf3988 internal nodes to settle, and the output to be within, say, 0.

It is obvious that the capacitor should have small leakage, so all electrolytics, whether aluminum or tantalum, are excluded. Apply an input voltage with a potentiometer, and watch the output voltage track it while the gate is connected to the drain.

The rise rate of the logic control should be greater than 1. Even if the times are taken into account, the accuracy of the output depends on several of398 parameters.

There is a settling time after the hold command until the output is within 1 mV of its steady value. The smaller the hold capacitor, the more quickly it can be charged and the smaller the acquisition time. This gain error is less than 0. When the control is changed to “hold,” below 1.

After the hold command, the aperture time is the time after which changes of the input voltage no longer affect the output voltage. The capacitor voltage changes as the dielectric “relaxes,” as well as when charge is supplied or taken away. This requires the opposed diodes that “catch” the output of the first op-amp when the feedback loop is broken in the “hold” state.

One change is that the feedback loop is extended from input to output. Note that we did not do much worse than this with our discrete circuit.


For most normal l3f98, a value of 0. The larger the hold capacitance, the smaller is the droop. Secondly, there is a finite jump in the output voltage called the hold step when the hold command is issued.

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Finally, there is droop as llf398 hold capacitor voltage declines steadily in the “hold” state. If you need better specs, there are the more expensive LF and LF which mainly give an extended temperature rangeand the LFA, with tightened specs. The next most important characteristic is “dielectric absorption” or hysteresis in the dielectric constant.

For us, we want to refer the logic to ground by connecting pin 7 to ground, and apply a positive input to pin 8 for the sample state.

The transition voltage is 1. Calvert Created 29 July Last revised 30 July The type of capacitor used is important. In the test, I used my debounced pushbutton for lt398 logic signal, choosing the normally-low output. What happens is this: I found that it took 28 minutes to decline to 0. The voltage kept on decreasing, until it reached some internal saturation value at