Texas Instruments OPA345UA

Overview

OPA345UA from Texas Instruments is a single, rail-to-rail input/output CMOS operational amplifier optimized for gain ≥ 5, with 3MHz gain-bandwidth product, 2V/µs slew rate, and 150µA typical quiescent current. It operates from 2.7V to 5.5V single supply and delivers 1mV output swing from rail into high-impedance loads - ideal for driving sampling ADCs in portable data acquisition systems.

For engineers reviewing the OPA345UA datasheet, OPA345UA pinout, OPA345UA application, or OPA345UA equivalent, this page provides verified specifications, SOIC-8 package terminal mapping, real-world use cases in audio and process control, and two validated alternative op amps with documented functional trade-offs.

Technical Context

The OPA345UA employs a complementary CMOS input stage enabling rail-to-rail common-mode input range (–0.3V to V+ + 0.3V) and a class-AB output stage delivering rail-to-rail output swing within 1mV at high open-loop gain. Its internal compensation targets stability at closed-loop gains ≥ 5.

It features ultra-low input bias current (±0.2pA typ), 30nV/√Hz input voltage noise density at 10kHz, and 0.006% THD+N at 1kHz with G = 5 - making it suitable for precision, low-power signal conditioning where input impedance and distortion matter.

Key Specifications

Pinout & Package

OPA345UA is supplied in an 8-pin SOIC (SO-8) surface-mount package (Package Drawing D), with thermal resistance θ_JA = 150°C/W. Pin numbering follows standard SOIC convention: Pin 1 = NC, Pin 2 = –In, Pin 3 = +In, Pin 4 = V–, Pin 5 = NC, Pin 6 = NC, Pin 7 = Out, Pin 8 = V+.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar rail-to-rail, low-power operational amplifier applications.

Compared with OPA345UA, OPA344UA trades bandwidth and slew rate for guaranteed unity-gain stability, while MCP6002-E/SN offers lower quiescent current and dual-channel density but sacrifices rail-to-rail input capability - impacting design flexibility in single-supply sensor interfaces.

Availability

OPA345UA is available at Aetrix Electronics and suitable for PCMCIA card designs, portable data acquisition systems, and industrial process control modules requiring stable component supply, RoHS-compliant packaging, and long-term production continuity.

Supply support for OPA345UA 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 connectivity technologies, with over 50 years of innovation in precision analog ICs.

The OPA345UA belongs to TI's MicroAmplifier™ series - designed specifically for low-power, miniature, rail-to-rail signal conditioning in battery-operated and space-constrained applications.

FAQ

What is the minimum recommended supply voltage for reliable operation of the OPA345UA?

The OPA345UA is fully specified from 2.7V to 5.5V, with guaranteed operation down to 2.5V. At 2.7V, key parameters including gain-bandwidth (3MHz), slew rate (2V/µs), and output swing (1mV from rail) remain valid across –40°C to +85°C. Operating below 2.7V may reduce open-loop gain and increase offset voltage drift - verify performance in final system conditions using TI's SBOS107A datasheet.

Can the OPA345UA drive a 1000pF capacitive load in a G = 5 configuration?

Yes - the OPA345UA is optimized for gains ≥ 5 and can directly drive up to 250pF pure capacitive load with minimal overshoot. For 1000pF, stability requires external compensation: add a 10Ω–20Ω series resistor between output and load (per Figure 5 in SBOS107A), or use a small isolation resistor (e.g., 22Ω) with local 0.01µF bypass at the load. Do not omit supply decoupling - 0.01µF ceramic on both V+ and V– pins is mandatory.

Is the OPA345UA pin-compatible with the OPA344UA in SOIC-8 packages?

No - the OPA345UA and OPA344UA share the same SOIC-8 package outline and pin count, but their pin functions differ. OPA345UA uses Pins 1, 5, and 6 as No Connect; OPA344UA uses Pin 1 as Output, Pin 5 as V–, and Pin 6 as V+. Substituting one for the other without PCB revision will result in non-functional circuits. Always verify pin mapping against TI's official package drawings before replacement.

What is the maximum input voltage allowed beyond the supply rails for the OPA345UA?

The OPA345UA input terminals are diode-clamped to the supply rails. Input voltages exceeding V– by more than 0.5V or V+ by more than 0.5V must be current-limited to ≤10mA using a series resistor. Inputs below V– –0.3V risk output lockup - TI recommends Schottky clamping (e.g., IN5818) if signals dip below ground. This limitation applies regardless of whether the device is powered; always observe absolute maximum ratings in all operating and power-down states.

Does the OPA345UA support true rail-to-rail input common-mode range across its full temperature range?

Yes - the OPA345UA maintains a common-mode input range of –0.3V to V+ + 0.3V over –40°C to +85°C. However, CMRR degrades in the transition region near V+ – 1.3V (±0.4V process variation), where both N- and P-channel input pairs operate. For highest CMRR (>76dB), keep V_CM < V+ – 1.8V. The datasheet specifies CMRR at multiple V_CM ranges and temperatures - consult SBOS107A Table 1 for exact values.