Analog Devices Inc. LT1793ACS8#PBF

Overview

LT1793ACS8#PBF from Analog Devices (formerly Linear Technology) is a precision JFET-input operational amplifier optimized for ultra-low-noise, high-impedance transducer signal conditioning. It delivers 6 nV/√Hz input voltage noise density at 1 kHz, 0.8 fA/√Hz input current noise density, and 3 pA typical input bias current over full common-mode range - enabling sub-picoampere-level signal integrity in photodiode, hydrophone, and piezoelectric sensor front ends.

For engineers reviewing the LT1793ACS8#PBF datasheet, LT1793ACS8#PBF pinout, LT1793ACS8#PBF application, or LT1793ACS8#PBF equivalent, key selection criteria include verified 1.5 pF input capacitance, guaranteed 4.2 MHz gain-bandwidth product, 10¹³ Ω common-mode input resistance, ±13.2 V output swing into 10 kΩ, and unconditional stability with 1000 pF capacitive loads - all confirmed across ±5 V and ±15 V supply operation.

Technical Context

The LT1793ACS8#PBF employs a JFET differential input stage with matched gate structures to maintain sub-10 pA bias current across –10.5 V to +13.5 V common-mode voltage, eliminating input-stage phase reversal and enabling robust DC-coupled high-Z sensing. Its noise architecture combines low-voltage-noise JFETs with optimized current-noise suppression, yielding total input-referred noise minima at source impedances >50 kΩ.

It features fully tested 100% voltage noise (≤8 nV/√Hz), slew rate (3.4 V/µs), and gain-bandwidth (4.2 MHz), with offset voltage adjustable via external potentiometer (pin 1 & 8). The amplifier remains stable at unity gain with ≥1000 pF load capacitance without external compensation.

Key Specifications

Pinout & Package

LT1793ACS8#PBF is housed in an 8-lead plastic SOIC (S8) package with JEDEC MS-012AC footprint, 1.27 mm lead pitch, and 5.0 mm × 6.2 mm body dimensions. Thermal resistance θ_JA = 190°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar JFET-input op amp applications.

Compared with LT1792CS8#PBF and OPA140AIDR, the LT1793ACS8#PBF uniquely balances ultra-low voltage and current noise with full common-mode bias-current stability, offset adjustability, and guaranteed 1000 pF capacitive load drive - making it the only option meeting all four requirements simultaneously in high-precision transducer interfaces.

Availability

LT1793ACS8#PBF is available at Aetrix Electronics and suitable for photocurrent amplification, hydrophone signal conditioning, piezoelectric accelerometer front ends, instrumentation amplifier cores, and active filter design requiring stable component supply and long-term production continuity.

Supply support for LT1793ACS8#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. (acquired Linear Technology in 2017) designs high-performance analog, mixed-signal, and RF ICs for precision measurement, signal integrity, and power management.

The LT1793ACS8#PBF belongs to Linear's precision JFET op amp family, engineered specifically for low-noise, high-input-impedance sensor signal conditioning in test equipment, medical instrumentation, and geophysical sensing.

FAQ

What is the maximum capacitive load the LT1793ACS8#PBF can drive without instability?

The LT1793ACS8#PBF is unconditionally stable driving ≥1000 pF capacitive loads at unity gain, as verified in production testing and documented in the datasheet Figure 13 (Capacitive Load Handling). This eliminates the need for series isolation resistors or feedback capacitors in transimpedance or charge amplifier configurations, preserving signal fidelity and simplifying layout. No external compensation is required for stability with any capacitive load up to and including 1000 pF.

Does the LT1793ACS8#PBF require external offset nulling, and how is it implemented?

Yes, the LT1793ACS8#PBF provides dedicated offset null terminals (pins 1 and 8) for external trimming. A 10 kΩ to 200 kΩ potentiometer is connected with its wiper to pin 1 (V_OS ADJ –), one end to pin 8 (V_OS ADJ +), and the other end to V–. This configuration allows adjustment of input offset voltage to <1 mV after calibration. The LT1793ACS8#PBF datasheet confirms this method yields ±1.3 mV maximum residual offset with a 10 kΩ potentiometer.

How does the LT1793ACS8#PBF maintain low input bias current across the common-mode range?

The LT1793ACS8#PBF achieves stable 3 pA typical input bias current from –10.5 V to +13.5 V common-mode voltage by using a matched JFET input stage with symmetrical gate structures and optimized biasing. Unlike conventional JFET op amps whose IB rises sharply near supply rails, the LT1793ACS8#PBF's architecture prevents gate leakage modulation, ensuring current noise remains constant. This is validated in Figure 1 of the datasheet, showing IB variation <10% across the full CM range.

Can the LT1793ACS8#PBF operate from ±5 V supplies, and are all specifications guaranteed at that voltage?

Yes, the LT1793ACS8#PBF is fully specified and guaranteed for operation from ±5 V supplies. Key parameters including input offset voltage (0.45 mV max), input bias current (4 pA max), gain-bandwidth product (2.5 MHz min), and output swing (±12.9 V into 10 kΩ) are explicitly tested and guaranteed at ±5 V per the Electrical Characteristics table. This makes the LT1793ACS8#PBF suitable for low-power portable instrumentation without sacrificing precision.

What is the input capacitance of the LT1793ACS8#PBF, and why is it critical for transducer applications?

The LT1793ACS8#PBF has a measured input capacitance of 1.5 pF (typical), specified under ±5 V and ±15 V supplies. This low value is critical because it minimizes phase shift and gain peaking when buffering high-impedance capacitive transducers (e.g., piezoelectrics, MEMS microphones), preserving frequency response linearity and stability. At 1.5 pF, the LT1793ACS8#PBF enables clean 100 kHz bandwidth in unity-gain buffer configurations - a key advantage over alternatives with >3 pF input capacitance.