Texas Instruments LM675T

Overview

LM675T from Texas Instruments is a monolithic power operational amplifier in a TO-220 (NDH) 5-pin package, delivering >3 A output current, ±25 V output swing into 8 Ω, and 5.5 MHz gain bandwidth. It operates from ±16 V to ±30 V supplies, features internal thermal shutdown with parole circuit, short-circuit protection, and is internally compensated for gains ≥10 - used in high-current servo amplifiers and motor speed controls.

For engineers reviewing the LM675T datasheet, LM675T pinout, LM675T application, or LM675T equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, application-specific implementation insights, and two confirmed alternative parts with documented functional and packaging differences.

Technical Context

The LM675T implements a fully integrated power op-amp architecture with bipolar input stage, Class AB output stage, and on-die current-limiting plus thermal protection circuitry that activates at 170°C junction temperature and resets at ~145°C. Its internal compensation ensures stability at closed-loop gains ≥10 without external components.

It includes built-in output clamp diodes connected between output and supply rails, enabling safe operation with reactive loads like motors and loudspeakers without external protection. Input common-mode range extends to ±22 V at ±25 V supplies, supporting wide-swing signal conditioning in industrial control loops.

Key Specifications

Pinout & Package

LM675T uses the TO-220 (NDH) 5-pin plastic power package with metal tab internally connected to Pin 3 (V−). The tab serves as both mechanical mounting surface and electrical connection to negative supply rail - requires insulated mounting hardware when V− is not chassis ground.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power operational amplifier applications.

Compared with LM675T/NOPB, the LM675T offers identical performance in legacy non-RoHS systems, while LM12CL trades integration for raw power capability - making LM675T optimal for space-constrained 3 A servo and audio amplifier designs requiring self-protected operation.

Availability

LM675T is available at Aetrix Electronics and suitable for motor speed controls, servo amplifiers, bridge audio amplifiers, and programmable power supplies requiring stable component supply across extended product lifecycles.

Supply support for LM675T 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 company headquartered in Dallas, Texas, designing and manufacturing analog ICs, embedded processors, and digital signal processors for industrial, automotive, and consumer markets.

The LM675T belongs to TI's legacy power op-amp product line, engineered for high-current linear amplification in industrial control, instrumentation, and audio systems where robustness, thermal resilience, and integrated protection are critical.

FAQ

What is the maximum continuous output current specification for LM675T?

The LM675T delivers more than 3 A of continuous output current into resistive loads with adequate heatsinking. Absolute maximum ratings specify ±30 V supply voltage and 30 W power dissipation at 70°C ambient. Internal current limiting activates near 4 A to protect the device during overload or short-circuit conditions, ensuring reliable operation without external current-sense circuitry.

Does LM675T require external compensation for unity-gain operation?

Yes, the LM675T is internally compensated for closed-loop gains of 10 or greater. For unity-gain or gains below 10, external compensation is required using a capacitor between the output and inverting input to maintain stability. Failure to compensate may result in high-frequency oscillation, especially with capacitive loads or poor PCB layout - refer to Figure 12 and Application Hints section of the SNOSBP3E datasheet for recommended values.

How is the metal tab on LM675T electrically connected, and what precautions apply?

The metal tab on LM675T is internally connected to Pin 3 (V−), which is the negative supply terminal. This means the tab must be electrically tied to the negative supply rail and cannot be left floating or grounded unless V− is at ground potential. When mounting to a heatsink, use an insulated mounting kit (e.g., mica washer + thermal grease) if the heatsink is chassis-grounded, to avoid shorting V− to system ground and damaging the device.

What thermal protection behavior does LM675T exhibit during sustained overload?

The LM675T features a thermal parole circuit: it shuts down at 170°C junction temperature and resumes operation only after cooling to ~145°C. If overheating persists, the restart threshold drops to 150°C to limit thermal cycling stress. This behavior is 100% tested without a heatsink. Proper heatsink selection - targeting ≤2.2°C/W total thermal resistance for 70°C ambient - is essential to avoid repeated shutdowns in continuous-duty applications.

Can LM675T drive highly capacitive loads, and what is the recommended mitigation?

The LM675T is not optimized for direct capacitive loading: oscillation occurs with >0.1 μF capacitance at the output without series resistance. To drive capacitive loads up to 2 μF safely, place ≥1 Ω series resistor between output and load. For reactive loads like loudspeakers, TI recommends a 10 Ω resistor in parallel with a 5 μH inductor at the output to damp high-frequency resonance - detailed in the APPLICATION HINTS section of the SNOSBP3E datasheet.