Texas Instruments LM346N

Overview

LM346N from Texas Instruments is a programmable quad operational amplifier designed for low-power, precision analog signal conditioning in battery-powered and space-constrained systems. It delivers 0.5 MHz minimum gain bandwidth product, 350 μA per amplifier supply current, and 28 nV/√Hz input voltage noise at ISET = 10 μA, enabling configurable trade-offs between speed, power, and noise in active filter and instrumentation circuits.

For engineers reviewing the LM346N datasheet, LM346N pinout, LM346N application, or LM346N equivalent, key selection criteria include its programmable GBW/slew rate via external ISET pins, ±1.5V to ±18V dual-supply operation, 0°C to +70°C industrial temperature range, SOIC-16 package compatibility, and use in capacitorless biquad filters requiring precise channel isolation.

Technical Context

The LM346N implements four independent, internally compensated op amps with programmable biasing via two external ISET pins (pins 8 and 9), allowing real-time adjustment of gain bandwidth product (0.5–1.2 MHz), slew rate (0.4 V/μs), supply current (140–300 μA per amplifier), input bias current (7.5–100 nA), and input noise. Its Class AB output stage eliminates crossover distortion while supporting rail-to-rail input common-mode range up to ±14 V at ±15 V supplies.

Unlike fixed-gain op amps, the LM346N's performance parameters scale linearly with ISET current - e.g., doubling ISET doubles GBW and slew rate while halving input noise power - enabling dynamic optimization for varying load, supply, or thermal conditions without changing the IC or PCB layout.

Key Specifications

Pinout & Package

LM346N is housed in a 16-pin SOIC (Package Drawing D), with 1.27 mm pitch, 10.3 mm × 7.5 mm body, and gull-wing leads. Pin 1 is marked by a beveled corner; the device features two dedicated programming terminals (pins 8 and 9) for ISET current injection, distinguishing it from standard quad op amp pinouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar programmable quad op amp applications.

Compared with LM146J, LM346N offers lower cost and SOIC packaging but sacrifices extended temperature and power handling; compared with LM324N, it trades fixed simplicity for runtime configurability of bandwidth, noise, and power - critical for adaptive sensor systems.

Availability

LM346N is available at Aetrix Electronics and suitable for portable instrumentation, active filter modules, voice-activated devices, and micropower sensor signal conditioning requiring stable component supply across production volumes.

Supply support for LM346N 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 and embedded processing technologies, with decades of innovation in precision op amps and power-efficient signal chains.

The LM346N belongs to TI's programmable op amp family, engineered specifically for applications demanding runtime-adjustable performance - such as battery-operated test equipment and adaptive filtering - where fixed-spec devices force design compromises.

FAQ

What is the maximum supply voltage for LM346N?

The LM346N supports a maximum dual supply voltage of ±18 V, as specified in its Absolute Maximum Ratings table. Exceeding this limit risks permanent damage to internal junctions. For reliable operation, maintain supply rails within ±1.5 V to ±18 V, with proper decoupling capacitors placed near pins 4 (V−) and 12 (V+) to suppress transients. The LM346N datasheet confirms this rating applies across its full 0°C to +70°C operating temperature range.

How does ISET current affect LM346N's gain bandwidth product?

The LM346N's gain bandwidth product scales linearly with ISET current: GBW = 1 MHz × (ISET / 10 μA). At ISET = 10 μA, GBW is 1 MHz (typ); at ISET = 5 μA, it drops to 0.5 MHz (min). This direct proportionality allows designers to reduce bandwidth and power simultaneously - for example, lowering ISET to 2 μA cuts GBW to 200 kHz and supply current to ~280 μA total for all four amplifiers. The LM346N schematic diagram shows ISET injected into pins 8 and 9 to enable this scaling.

Can LM346N be used in single-supply configurations?

Yes, the LM346N operates in single-supply mode with V+ tied to positive rail and V− grounded, provided input common-mode voltage remains within specification (e.g., 0.7 V above ground at ±1.5 V supply). Figure 31 in the LM346N datasheet illustrates a single-positive-supply biasing network using resistive dividers to establish mid-rail virtual ground. Output swing is limited to ~0.6 V from each rail under these conditions, making it suitable for low-voltage sensor interfaces but not rail-to-rail output applications.

What is the thermal resistance (θjA) of LM346N in SOIC package?

The LM346N in SOIC-16 package (Package Drawing D) has a junction-to-ambient thermal resistance (θjA) of 115°C/W, as documented in the Absolute Maximum Ratings section of its datasheet. This value assumes standard JEDEC 2-layer board conditions. At maximum ambient temperature (70°C) and 500 mW power dissipation, junction temperature reaches ~127°C - safely below the 100°C max junction limit only if derated; actual safe power must be calculated as Pd = (TjMAX − TA)/θjA = (100 − 70)/115 ≈ 260 mW.

Does LM346N support shutdown functionality?

Yes, the LM346N supports amplifier shutdown by pulling both ISET pins (8 and 9) to V− (negative supply or ground in single-supply mode). This action disables internal bias currents, forcing all four outputs into high-impedance state with leakage <100 nA. Figure 40 in the LM346N datasheet demonstrates this behavior, confirming it enables ultra-low-power sleep modes - ideal for intermittent-sampling systems like voice-activated recorders where amplifiers remain inactive >99% of the time.