Texas Instruments LF298M/NOPB

Overview

LF298M/NOPB from Texas Instruments is a monolithic BI-FET sample-and-hold IC operating as a unity-gain follower with 0.002% typical DC gain accuracy, ≤10 µs acquisition time to 0.1%, and 0.5 mV typical hold step at 0.01 µF hold capacitance. It serves as a precision analog signal capture stage in data acquisition systems requiring stable DC accuracy and low droop during hold.

For engineers reviewing the LF298M/NOPB datasheet, LF298M/NOPB pinout, LF298M/NOPB application, or LF298M/NOPB equivalent, key selection considerations include ±5 V to ±18 V dual-supply operation, TTL/CMOS-compatible logic interface with 1.4 V differential threshold, input impedance of 10¹⁰ Ω, and guaranteed performance over –25°C to +85°C ambient temperature.

Technical Context

The LF298M/NOPB uses a bipolar input stage combined with P-channel JFET output devices to achieve low offset voltage (≤3 mV typ), wide bandwidth (enabling stable inclusion inside 1-MHz op-amp feedback loops), and low droop rate (as low as 5 mV/min with 1 µF capacitor). Its BI-FET architecture ensures input characteristics remain unchanged during hold mode, eliminating feedthrough even for input signals at supply rails.

Functional operation is controlled by a fully differential logic interface: device enters sample mode when LOGIC pin is ≥1.4 V above LOGIC REFERENCE, and hold mode when LOGIC is ≤1.4 V below it. Offset adjustment is performed via a dedicated pin without degrading drift performance, and leakage into the hold capacitor is limited to 100 pA max at 25°C.

Key Specifications

Pinout & Package

LF298M/NOPB is housed in a 14-pin SOIC (D package) with nominal body size 8.65 mm × 3.91 mm. The package is RoHS-compliant and lead-free (NOPB suffix).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar sample-and-hold applications.

Compared with LF298M/NOPB, LF398N/NOPB trades precision for lower cost and ease of through-hole assembly, while LF198N/NOPB adds extended temperature capability and military screening at the expense of higher price and larger footprint - all three share identical functional architecture and pin-compatible logic interface.

Availability

LF298M/NOPB is available at Aetrix Electronics and suitable for instrumentation data acquisition, automated test equipment, programmable ramp generation, and synchronous correlator designs requiring stable component supply across production lifecycles.

Supply support for LF298M/NOPB includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company specializing in analog and embedded processing technologies, with leadership in precision signal chain components.

The LFx98x family-including LF298M/NOPB-is designed for high-fidelity analog signal capture in test, measurement, and industrial control systems where DC accuracy, low droop, and fast acquisition are essential.

FAQ

What is the maximum recommended hold capacitor value for LF298M/NOPB?

The LF298M/NOPB datasheet does not specify an absolute maximum hold capacitor value, but practical limits arise from acquisition time and drive capability. With a 1 µF capacitor, acquisition time increases to ~200 µs, and the internal 300 Ω series resistor may cause excessive self-heating at high repetition rates. For optimal performance, TI recommends 0.001 µF to 0.1 µF. Larger values (up to 1 µF) are usable if longer acquisition time and thermal management are acceptable - the LF298M/NOPB itself remains functional across this range.

Does LF298M/NOPB support single-supply operation?

No, LF298M/NOPB requires dual symmetric supplies (e.g., ±12 V or ±15 V) to operate within its specified input and output voltage ranges. Its input common-mode range is –VS + 3.5 V to +VS – 3.5 V, and output swing is similarly rail-referenced. Attempting single-supply operation (e.g., 0 V and +15 V) violates absolute maximum ratings and results in undefined behavior, including potential damage. For single-supply applications, consider purpose-built alternatives such as the TLC549 or MAX197 - the LF298M/NOPB is strictly a dual-supply device.

How does the OFFSET ADJUST pin function in LF298M/NOPB?

The OFFSET ADJUST pin on LF298M/NOPB connects to the wiper of a 1 kΩ potentiometer whose ends are tied to V+ and ground (via a current-setting resistor). This configuration injects a small correction current into the input stage to null input offset voltage - typically reducing it from ≤3 mV to <0.5 mV. Critically, TI specifies that this adjustment does not degrade input offset drift over temperature, making it suitable for precision DC-coupled systems. The LF298M/NOPB's internal circuitry ensures the trim remains stable across –25°C to +85°C ambient.

Can LF298M/NOPB be used with ceramic hold capacitors?

Yes, LF298M/NOPB can be used with NP0/C0G ceramic capacitors, which exhibit low dielectric absorption (<0.1%) and stable capacitance over temperature and voltage. These are preferred over X7R or Y5V types, which introduce hysteresis errors up to 1% and cause significant hold-step distortion. TI explicitly recommends polystyrene, polypropylene, Teflon, and NP0/C0G ceramics for high-accuracy applications. When using NP0/C0G, ensure rated voltage exceeds peak hold voltage and derate for DC bias effects - the LF298M/NOPB's 100 pA leakage spec remains valid with these dielectrics.

What is the logic input voltage range for reliable operation of LF298M/NOPB?

For reliable sample/hold mode switching, the LF298M/NOPB requires the LOGIC pin voltage to differ from LOGIC REFERENCE by at least ±1.4 V (differential threshold), with recommended margins: LOGIC HIGH ≥ +2.5 V above LOGIC REFERENCE, LOGIC LOW ≤ –2.5 V below it. TI specifies that proper logic operation requires one logic pin to be at least 2 V below V+ and 3 V above V−. Thus, with ±15 V supplies, LOGIC must stay within –12 V to +13 V. Exceeding these bounds risks latch-up or permanent damage - the LF298M/NOPB's logic interface is robust but not rail-to-rail tolerant.