LF398-N: Low cost Sample and Hold Amplifier from TI

Hello Mahabir,

Here are some answers to you S/H questions:

1. Why does not TI has Sample and Hold Amplifiers? They have one from NSC folio, LF398 without a hold capacitor.

In earlier A-to-D designs the often required that a S/H amplifier be added in front to acquire and hold an input voltage. Over time the function was integrated into the A-to-D converters and the demand for S/H amplifiers dwindled. Availability of any particular IC is highly dependent on demand for the function. The LM398 is a legacy S/H and what demand we see for such products is usually satisfied by the device. The capacitor is external so that the user can select a value that is best suited for the particular hold time and droop behavior.

2. From other Vendors, AD and Renesas (Intersil) have multiple good devices, but very costly, why they are so costly? For example - AD781/83 from ADI and HA5153 from Intersil.

I can only speculate that our competitors marketing and pricing practices for their products is based on the cost to produce those products and their demand.  

3. Does TI has a plan to bring a new chip in this area?

I do not know of any from TI as it presents a very limited market opportunity.

4. Can someone suggest to me, low-cost IC, +/- Input, less or equal to 1 usec acquisition time, single channel device

Unfortunately, TI's LF398 doesn't meet the requirements. It is best for other suppliers to comment on their products.

Regards, Thomas

Precision Amplifiers Applications Engineering