LF198-N_16 Datasheet, PDF (1/33 Pages) Texas Instruments – Monolithic Sample-and-Hold Circuits

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LF198-N, LF298, LF398-N
LF198A-N, LF398A-N
SNOSBI3B – JULY 2000 – REVISED NOVEMBER 2015
LF298, LFx98x Monolithic Sample-and-Hold Circuits
1 Features
•1 Operates from ±5-V to ±18-V Supplies
• Less than 10-μs Acquisition Time
• Logic Input Compatible With TTL, PMOS, CMOS
• 0.5-mV Typical Hold Step at Ch = 0.01 µF
• Low Input Offset
• 0.002% Gain Accuracy
• Low Output Noise in Hold Mode
• Input Characteristics Do Not Change During Hold
Mode
• High Supply Rejection Ratio in Sample or Hold
• Wide Bandwidth
• Space Qualified, JM38510
2 Applications
• Ramp Generators With Variable Reset Level
• Integrators With Programmable Reset Level
• Synchronous Correlators
• 2-Channel Switches
• DC and AC Zeroing
• Staircase Generators
3 Description
The LF298 and LFx98x devices are monolithic
sample-and-hold circuits that use BI-FET technology
to obtain ultrahigh 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-N to be
included inside the feedback loop of 1-MHz
operational amplifiers without having stability
problems. Input impedance of 10¹⁰ Ω allows high-
source impedances to be used without degrading
accuracy.
P-channel junction FETs 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
JFETs have much lower noise than MOS devices
used in previous designs and do not exhibit high
temperature instabilities. The overall design ensures
no feedthrough from input to output in the hold mode,
even for input signals equal to the supply voltages.
Logic inputs on the LF198-N are fully differential with
low input current, allowing for direct connection to
TTL, PMOS, and CMOS. Differential threshold is
1.4 V. The LF198-N will operate from ±5-V to ±18-V
supplies.
An A version is available with tightened electrical
specifications.
Typical Connection
Device Information⁽¹⁾
PART NUMBER
PACKAGE
BODY SIZE (NOM)
SOIC (14)
8.65 mm × 3.91 mm
LF298, LFx98x
TO-99 (8)
9.08 mm × 9.08 mm
PDIP (8)
9.81 mm × 6.35 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Acquisition Time
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.