LF398

The LF198/LF298/LF398 are monolithic sample-and-hold circuits which utilize BI-FET technology to obtain ultra-high dc accuracy with fast acquisition of signal and low droop rate. Operating as a unity gain follower, dc gain accuracy is 0.002% typical and acquisition time is as low as 6 µs to 0.01%. A bipolar input stage is used to achieve low offset voltage and wide bandwidth. Input offset adjust is accomplished with a single pin, and does not degrade input offset drift. The wide bandwidth allows the LF198 to be included inside the feedback loop of 1 MHz op amps without having stability problems. Input impedance of 1010Ohm allows high source impedances to be used without degrading accuracy.

P-channel junction FET's are combined with bipolar devices in the output amplifier to give droop rates as low as 5 mV/min with a 1 µF hold capacitor. The JFET's have much lower noise than MOS devices used in previous designs and do not exhibit high temperature instabilities. The overall design guarantees no feed-through from input to output in the hold mode, even for input signals equal to the supply voltages.

Reliability Metrics

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Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LF398 MDC	BIFET	0	12335	0	0	975000	4	276658912
LF398 MWC	BIFET	0	12335	0	0	975000	4	276658912
LF398AH	BIFET	0	12335	0	0	975000	4	276658912
LF398AN	BIFET	0	12335	0	0	975000	4	276658912
LF398H	BIFET	0	12335	0	0	975000	4	276658912
LF398M	BIFET	0	12335	0	0	975000	4	276658912
LF398MX	BIFET	0	12335	0	0	975000	4	276658912
LF398N	BIFET	0	12335	0	0	975000	4	276658912

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

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Application Notes

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Title	Size in Kbytes	Date
AN-298: Application Note 298 Isolation Techniques for Signal Conditioning	379 Kbytes	2-Oct-02	Download
AN-775: Specifications and Architectures of Sample-and-Hold Amplifiers	111 Kbytes	5-Aug-95	Download
AN-775 (Japanese): Specifications and Architectures of Sample-and-Hold Amplifiers	251 Kbytes
AN-266: Application Note 266 Circuit Applications of Sample-Hold Amplifiers	508 Kbytes	2-Oct-02	Download
AN-258: Application Note 258 Data Acquisition Using the ADC0816 and ADC0817 8-Bit A/D Converter with On-Chip 16 Channel Multiplexer	683 Kbytes	4-Oct-04	Download
AN-301: Application Note 301 Signal Conditioning for Sophisticated Transducers	579 Kbytes	2-Oct-02	Download
AN-247: Application Note 247 Using the ADC0808/ADC0809 8-Bit µP Compatible A/D Converters with 8-Channel Analog Multiplexer	547 Kbytes	3-Oct-02	Download

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More Application Notes

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Title	Size in Kbytes	Date
AN-292: Application Note 292 Applications of the LM3524 Pulse-Width-Modulator	239 Kbytes	3-Oct-02	Download

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