LF256H

Overview

The LF256H is a single J-FET input operational amplifier manufactured by Texas Instruments, formerly National Semiconductor. It features a gain-bandwidth product of 5 MHz and a slew rate of 12 V/us. The device operates on a supply voltage range of 10 V to 44 V (±5 V to ±22 V) with a typical operating current of 5 mA per channel. Key electrical specifications include an input offset voltage of 2 mV, input bias current of 100 pA, and input noise current density of 10 fA/sqrt Hz. It provides a common-mode rejection ratio of 100 dB and power supply rejection ratio of 85 dB. The component is housed in a TO-99-8 metal can package for through-hole mounting.

Feature Summary

• Monolithic integration of well-matched high-voltage J-FETs with standard bipolar transistors on the same chip
• Offset adjustment capability that does not degrade drift or common-mode rejection performance
• Internal compensation combined with large differential input voltage capability up to the positive supply rail

Applications

• Precision high-speed integrators
• Fast D/A converters
• High impedance buffers
• Wideband low noise amplifiers
• Sample and hold circuits

Procurement Notes

Verify the manufacturer designation as Texas Instruments, which acquired National Semiconductor's analog portfolio. Confirm the specific suffix 'H' corresponds to the TO-99-8 metal can package variant rather than plastic packages. Ensure RoHS compliance status matches project requirements, as older datasheets may list non-compliant variants. Cross-reference the part number against official TI documentation to confirm pinout compatibility with legacy designs.

Selection Notes

Select this component when high input impedance and low bias current are required alongside moderate bandwidth. The internal offset adjust feature makes it suitable for precision applications where drift stability is critical. Compare against the LF356 series if lower cost or different packaging is preferred, noting potential differences in noise characteristics and offset adjust functionality. Ensure the supply voltage range aligns with the system's power rails.

Part Context

The LF256 belongs to the LFx5x family of J-FET input operational amplifiers originally developed by National Semiconductor. This family is characterized by combining J-FET input stages with bipolar processing for improved matching and speed. The LF256H specifically denotes the hermetically sealed metal can version, often used in military or high-reliability aerospace applications requiring robust environmental protection compared to standard plastic packaged equivalents.

Replacement Considerations

• LF356M/NOPB
• LF256

FAQ

Does the offset adjust feature affect common-mode rejection?

No, the design ensures that offset adjustment does not degrade drift or common-mode rejection, unlike most monolithic amplifiers.

What is the maximum differential input voltage?

The device supports a large differential input voltage capability up to the positive supply voltage (VCC+).