Texas Instruments LF298H/NOPB

Overview

LF298H/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 functions in ±5 V to ±18 V supplies and serves precision data acquisition systems requiring low droop, high input impedance (10¹⁰ Ω), and TTL/CMOS-compatible logic control.

For engineers reviewing the LF298H/NOPB datasheet, LF298H/NOPB pinout, LF298H/NOPB application, or LF298H/NOPB equivalent, key selection criteria include hold capacitor leakage current (≤100 pA), feedthrough attenuation (≥86 dB at 1 kHz), output impedance in hold mode (≤2 Ω), differential logic threshold (1.4 V), and junction temperature limit (85°C).

Technical Context

The LF298H/NOPB implements a bipolar-input/JFET-output BI-FET architecture: a high-impedance bipolar front-end ensures low offset voltage and wide bandwidth, while P-channel JFETs in the output stage minimize droop rate (as low as 5 mV/min with 1 µF) and thermal instability. Its fully differential logic interface accepts TTL, PMOS, and CMOS signals with 1.4 V threshold and supports direct connection without level-shifting.

Functional operation is strictly dual-mode: sample mode enables output tracking of input via hold capacitor charging/discharging; hold mode disconnects the input path and maintains output voltage using the charged capacitor. Input offset is adjustable via a dedicated pin without degrading drift performance, and the device remains stable inside feedback loops of up to 1-MHz op-amps.

Key Specifications

Pinout & Package

LF298H/NOPB is housed in an 8-pin TO-99 metal can package (9.08 mm × 9.08 mm), rated for operation from –25°C to +85°C ambient temperature and featuring hermetic sealing suitable for demanding environments.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LF298H/NOPB, LF398N/NOPB trades lower cost and broader commercial availability for reduced DC accuracy and higher leakage, while AD585SQ delivers superior precision and qualification at the expense of non-interchangeable packaging and stricter supply constraints.

Availability

LF298H/NOPB is available at Aetrix Electronics and suitable for high-reliability test equipment, aerospace instrumentation, and industrial process controllers requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for LF298H/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 leader specializing in analog, embedded processing, and power management technologies, with decades of heritage in precision linear ICs.

The LFx98x family-including LF298H/NOPB-was designed specifically for high-fidelity sample-and-hold applications in data acquisition, instrumentation, and signal processing systems demanding ultralow droop, fast acquisition, and exceptional DC accuracy.

FAQ

What is the maximum operating temperature for LF298H/NOPB?

The LF298H/NOPB is rated for operation from –25°C to +85°C ambient temperature. Its junction temperature must not exceed 115°C, and thermal derating applies above 70°C ambient per the R_θJA value of 85°C/W. This makes LF298H/NOPB suitable for industrial enclosures and non-hermetic avionics bays where airflow is limited but ambient stays within spec.

Can LF298H/NOPB operate from a single +15 V supply?

No, LF298H/NOPB requires dual symmetric supplies (e.g., ±5 V to ±18 V) and cannot function on a single-ended rail. The internal BI-FET architecture depends on balanced positive and negative supply paths for proper biasing of both input and output stages. Attempting single-supply operation will result in undefined behavior or damage.

What hold capacitor value is recommended for optimal acquisition time and droop trade-off in LF298H/NOPB?

For general-purpose use, 0.01 µF is the standard value specified in the LF298H/NOPB datasheet - yielding ≤10 µs acquisition time and 0.5 mV typical hold step. Larger values (e.g., 0.1–1 µF) reduce droop rate but increase acquisition time; smaller values (<1000 pF) improve speed but raise hold step and susceptibility to stray coupling. Polypropylene or C0G ceramic capacitors are preferred for low dielectric absorption.

Does LF298H/NOPB support CMOS logic inputs directly?

Yes, LF298H/NOPB's fully differential logic interface accepts CMOS signals directly: for 3–7 V logic-high swing, the threshold is fixed at 1.4 V; for 7–15 V swings, it scales to 0.6×V₊ ±1.4 V. No external level-shifting or pull-up resistors are needed - simply tie LOGIC REFERENCE to system ground and drive LOGIC with standard CMOS outputs.

How does the OFFSET ADJUST pin function in LF298H/NOPB?

The OFFSET ADJUST pin in LF298H/NOPB connects to the wiper of a 1-kΩ potentiometer whose ends are tied to V+ and ground (via a current-setting resistor). Adjusting the wiper nulls input offset voltage without degrading temperature drift performance - a key advantage over amplifier-based trimming methods. This allows factory or field calibration to <1 mV residual offset.