Analog Devices Inc. LTC6268IS8-10#PBF

Overview

LTC6268IS8-10#PBF from Analog Devices (formerly Linear Technology) is a single-channel, decompensated FET-input operational amplifier optimized for ultra-high-speed transimpedance amplification with femtoamp-level input bias current. It delivers 4GHz gain-bandwidth product, ±3fA typical input bias current at room temperature, 0.45pF common-mode input capacitance, rail-to-rail output swing, and operates from 3.1V to 5.25V supply. It is widely deployed in photomultiplier tube post-amplifiers and low-leakage sensor interfaces requiring sub-picoamp signal integrity.

For engineers reviewing the LTC6268IS8-10#PBF datasheet, LTC6268IS8-10#PBF pinout, LTC6268IS8-10#PBF application, or LTC6268IS8-10#PBF equivalent, key selection criteria include its gain-of-10 stability, shutdown functionality, SOIC-8 package with guard-ring-capable NC pins, and verified performance in high-impedance, wideband TIA designs up to 210MHz closed-loop bandwidth.

Technical Context

The LTC6268IS8-10#PBF employs a CMOS input buffer stage that bootstraps protection diodes to minimize leakage, followed by a complementary differential pair active across the full input common-mode range (–0.1V to 4.5V). Its decompensated architecture requires minimum noise-gain ≥10 for stability, enabling high closed-loop bandwidths when paired with low-input-capacitance photodiodes or sensors.

It integrates an active-low SHDN pin with 0.75V logic threshold, delivering 360ns turn-on and 183ns turn-off delays. The output stage uses a common-emitter topology to achieve rail-to-rail swing while maintaining +1500V/µs slew rate (positive edge) and –1000V/µs (negative edge) under 500Ω load.

Key Specifications

Pinout & Package

The LTC6268IS8-10#PBF is housed in an 8-lead plastic SOIC (S8) package with two unconnected pins (Pin 5 and Pin 8) usable as guard rings to suppress PCB surface leakage. Thermal resistance θ_JA = 120°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultra-low-bias-current, high-speed op amp applications.

Compared with ADA4817-1ARMZ and LTC6268HS8-10#PBF, the LTC6268IS8-10#PBF uniquely balances 4GHz bandwidth, ±3fA bias current, 0.45pF input capacitance, and integrated shutdown in an industrial-temperature SOIC-8-making it optimal for cost-sensitive, high-speed, low-leakage instrumentation where 125°C rating is unnecessary.

Availability

LTC6268IS8-10#PBF is available at Aetrix Electronics and suitable for photomultiplier tube post-amplification, high-speed transimpedance amplification, and low-leakage sensor interfacing requiring stable component supply across industrial temperature ranges.

Supply support for LTC6268IS8-10#PBF 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

Analog Devices, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, acquired Linear Technology in 2017 to strengthen its precision amplifier portfolio.

The LTC6268-10 family was designed specifically for ultra-low-input-bias-current, high-speed applications such as photodetection, scientific instrumentation, and precision sensor signal conditioning-prioritizing femtoamp leakage control and GHz-class bandwidth in compact packages.

FAQ

What is the minimum stable gain for LTC6268IS8-10#PBF?

The LTC6268IS8-10#PBF is decompensated and specified as gain-of-10 stable. It requires a minimum noise gain of 10 (e.g., non-inverting gain ≥10 or inverting gain magnitude ≥9) to ensure unity-gain stability margin. Operating at lower gains risks oscillation unless external compensation is applied per the datasheet's CF guidelines.

Does LTC6268IS8-10#PBF support split-supply operation?

Yes, LTC6268IS8-10#PBF supports split supplies as long as the total voltage between V+ and V– remains within 3.1V to 5.25V. For example, ±2.5V (5V total) or +3.3V/–1.2V (4.5V total) are valid. Input common-mode range extends from V– to V+–0.5V, and output swings rail-to-rail relative to V+ and V–.

How does the NC pin configuration benefit LTC6268IS8-10#PBF in low-leakage designs?

The two NC pins (Pin 5 and Pin 8) on the LTC6268IS8-10#PBF SOIC-8 package can be routed as continuous guard rings surrounding the +IN and –IN traces. This actively shunts surface leakage currents away from the high-impedance input nodes, preserving the ±3fA input bias current specification in humid or contaminated environments.

What is the maximum recommended feedback capacitance (CF) for a 20kΩ TIA using LTC6268IS8-10#PBF?

For a 20kΩ transimpedance amplifier, the LTC6268IS8-10#PBF datasheet specifies a CF range of 60fF to 100fF when total input capacitance (C_IN) is 1pF. This CF value damps the feedback pole formed by RF||C_IN, ensuring stability while maximizing bandwidth-exceeding 100fF risks excessive peaking or reduced phase margin.

Is LTC6268IS8-10#PBF pin-compatible with other variants in the LTC6268-10 family?

Yes, all LTC6268-10 variants-including LTC6268IS8-10#PBF, LTC6268HS8-10#PBF, and LTC6268IS6-10#TRPBF-share identical pinouts for their respective packages. The SOIC-8 versions (e.g., LTC6268IS8-10#PBF) have consistent Pin 1–8 assignments regardless of temperature grade or packaging suffix, enabling drop-in replacement within the same package footprint.