LF398M/NOPB

The LFx98x devices are monolithic sample-and-hold circuits using BI-FET technology, achieving ultra-high DC accuracy through fast signal acquisition and low droop rate. As a unity-gain follower, the DC gain accuracy is 0.002% (typical), and the acquisition time is as low as 6μs (0.01%). A bipolar input stage is used to achieve low offset voltage and wide bandwidth. Input offset adjustment is accomplished via a single pin without degrading the input offset drift. The wide bandwidth allows the LFx98x to be included in the feedback loop of a 1MHz operational amplifier without stability issues. The input impedance is 10^10Ω, allowing the use of high source impedance without degrading accuracy. The combination of P-channel junction FETs with bipolar devices in the output amplifier provides a droop rate as low as 5mV/min through a 1μF hold capacitor. The noise of JFETs is significantly lower than that of MOS devices used in previous designs, and there is no high-temperature instability. The overall design ensures no input-to-output feedthrough in the hold mode, even when the input signal equals the supply voltage. The logic inputs on the LFx98x are completely different with low input current, allowing direct connection to TTL, PMOS, and CMOS. The differential threshold is 1.4V. The LFx98x is powered by supplies from ±5V to ±18V. The A version offers more stringent electrical specifications.

Applications

• Ramp generator with variable reset level
• Integrator with programmable reset level
• Synchronous correlator
• Dual-channel switch
• DC and AC return-to-zero staircase generator

Key features

• Operates from ±5V to ±18V supplies
• Acquisition time less than 10μs
• Logic inputs compatible with TTL, PMOS, CMOS
• Hold step of 0.5mV (typical) at Ch = 0.01μF
• Low input offset
• Gain accuracy of 0.002%
• Low output noise in hold mode
• Input characteristics unchanged during hold mode
• High power supply rejection ratio in sample or hold mode
• Wide bandwidth
• Space qualified, compliant with JM38510