Analog Devices Inc. AD8684ARUZ

Overview

AD8684ARUZ from Analog Devices is a quad-channel, low-power, precision JFET-input operational amplifier optimized for high-speed, low-quiescent-current operation in battery-powered and portable instrumentation. It delivers 9 V/μs slew rate, 3.5 MHz gain bandwidth, ≤1 mV offset voltage at 25°C, 20 pA max input bias current, and operates from ±4.5 V to ±18 V supplies - enabling high-accuracy signal conditioning in high-impedance sensor interfaces.

For engineers reviewing the AD8684ARUZ datasheet, AD8684ARUZ pinout, AD8684ARUZ application, or AD8684ARUZ equivalent, key selection criteria include its rail-to-rail input common-mode range (−11 V to +15 V), unity-gain stability, low noise (36 nV/√Hz), and guaranteed performance across −40°C to +85°C for portable medical, loop filter, and strain gauge amplifier designs.

Technical Context

The AD8684ARUZ employs a JFET input stage to achieve ultra-low input bias current (<125 pA over temperature) and high input impedance (>10¹² Ω), making it suitable for high-source-impedance applications like piezoelectric sensors and photodiode amplifiers. Its unity-gain stable architecture supports direct use in noninverting configurations with capacitive loads up to 500 pF without oscillation.

It features fast settling (1.6 μs to 0.01%), high PSRR (114 dB), and CMRR (90 dB typical), ensuring robust performance in noisy industrial environments. The device maintains dc precision - including <3.5 mV max offset over +25°C to +85°C - while drawing only 250 μA per amplifier, balancing speed and power efficiency.

Key Specifications

Pinout & Package

AD8684ARUZ is packaged in a 14-lead TSSOP (RU-14) with exposed pad, offering compact footprint (5.0 mm × 4.4 mm) and thermal resistance θ_JA = 180°C/W, suitable for space-constrained PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL074CDR and OPA4134UA, AD8684ARUZ uniquely balances sub-250 μA quiescent current, <1 mV offset, and 9 V/μs slew rate - making it the only option among the three qualified for portable, precision, high-impedance analog front-ends operating continuously on primary cells.

Availability

AD8684ARUZ is available at Aetrix Electronics and suitable for portable medical instrumentation, strain gauge amplifiers, loop filters, and active precision filters requiring stable component supply across extended production lifecycles.

Supply support for AD8684ARUZ 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. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD868x family was designed specifically for low-power, high-precision signal conditioning in portable and battery-operated instrumentation - emphasizing JFET input performance, rail-compatible common-mode range, and unity-gain stability without external compensation.

FAQ

What is the maximum operating temperature range for AD8684ARUZ?

The AD8684ARUZ is specified to operate from −40°C to +85°C. This industrial temperature range is validated across all electrical parameters in the datasheet, including input offset voltage (max 4 mV at −40°C to +25°C), supply current (250 μA/amp max), and CMRR (70 dB min). The device uses standard silicon process technology and does not require derating below −40°C or above +85°C for functional operation.

Does AD8684ARUZ support rail-to-rail input operation?

Yes, AD8684ARUZ supports rail-to-rail input operation within a common-mode voltage range of −11 V to +15 V when powered from ±15 V supplies. This includes operation at the positive rail (+15 V), enabling high-side current sensing without level-shifting circuitry. The input stage is JFET-based, so it does not exhibit phase inversion until V_CM exceeds +15 V or falls below −11 V - both outside the specified operating range.

Can AD8684ARUZ drive capacitive loads without instability?

Yes, AD8684ARUZ is unity-gain stable and can drive capacitive loads up to 500 pF with minimal overshoot (<10%) when configured in noninverting unity-gain mode (G = 1). Figure 5 in the datasheet confirms this behavior with RL = 2 kΩ. For loads >500 pF, a series resistor (≥100 Ω) between the output and capacitance is recommended to maintain phase margin >45° and prevent peaking.

What package type is used for AD8684ARUZ?

AD8684ARUZ is supplied in a 14-lead Thin Shrink Small Outline Package (TSSOP), designated RU-14 per Analog Devices' ordering guide. Its dimensions are 5.0 mm × 4.4 mm × 1.2 mm, with 0.65 mm lead pitch and an exposed thermal pad. This package offers lower thermal resistance (θ_JA = 180°C/W) than SOIC_N alternatives and is RoHS-compliant (Z suffix).

Is AD8684ARUZ pin-compatible with other quad op amps like LM324 or TL074?

No, AD8684ARUZ is not pin-compatible with LM324 or TL074. It follows the standard 14-lead TSSOP pinout for quad op amps (OUT A, –IN A, +IN A, V+, +IN B, –IN B, OUT B, OUT C, –IN C, +IN C, V–, +IN D, –IN D, OUT D), whereas LM324 uses a different pin mapping (e.g., V– is pin 11, not pin 11 in AD8684ARUZ). Substituting without PCB revision will cause functional failure due to misrouted supplies and inputs.