Texas Instruments LM306D

Overview

LM306D from Texas Instruments is a high-speed voltage comparator with differential inputs, 100 mA high-sink-current open-collector output, dual strobe inputs, and operation from −3 V to −12 V negative supply (with +12 V positive rail). It delivers 40 ns low-to-high response time, ±5 mV input offset voltage max at 25°C, and drives up to 10 TTL loads directly. Used in precision threshold detection circuits for industrial control and power supply monitoring.

For engineers reviewing the LM306D datasheet, LM306D pinout, LM306D application, or LM306D equivalent, key selection considerations include strobe-controlled output gating, wide common-mode input range (±5 V), short-circuit protection, and compatibility with legacy 54/74 TTL logic families.

Technical Context

The LM306D implements a bipolar transistor-based comparator architecture with two independent strobe inputs that force high-impedance output state when asserted low. Its differential input stage supports common-mode voltages from −12 V to +5 V relative to ground, and its output stage uses a high-current NPN sink capable of 100 mA continuous current.

Strobe logic is active-low: either STROBE 1 or STROBE 2 pulled low overrides the differential input and holds OUT high; only when both strobes are open or high does the output respond to IN+ vs IN−. The device operates with asymmetric dual supplies - VCC+ = +12 V typical, VCC− = −3 V to −12 V - and exhibits stable performance across that full negative rail range.

Key Specifications

Pinout & Package

LM306D is supplied in an 8-pin SOIC (Small Outline Integrated Circuit) package, 3.9 mm width, 1.75 mm max height, RoHS-compliant with NIPDAU lead finish and JEDEC MS-012 AA outline.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage comparator applications.

Compared with LM306D, LM311DR offers wider supply flexibility but slower response and no strobe control, while LM393DR reduces power and doubles channel count at the cost of drive strength and gating capability - making LM306D uniquely suitable for strobe-synchronized, high-current industrial comparator roles.

Availability

LM306D is available at Aetrix Electronics and suitable for industrial control systems, power supply protection circuits, and legacy TTL interface design requiring stable component supply and long-term obsolescence management.

Supply support for LM306D 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 founded in 1930, specializing in analog, embedded processing, and power management ICs for industrial, automotive, and communications markets.

The LM306D belongs to TI's legacy linear comparator product line, designed specifically for high-speed, high-drive industrial signal conditioning and fault detection where strobe-controlled output blanking and robust negative-rail operation are required.

FAQ

What is the maximum negative supply voltage rating for LM306D?

The LM306D supports a VCC− supply voltage up to −15 V, as specified in its Absolute Maximum Ratings table. However, recommended operation is between −3 V and −12 V, where performance parameters including gain, offset, and response time remain stable and within datasheet limits. Exceeding −12 V may increase power dissipation and affect long-term reliability, though the device will not be damaged until −15 V is reached.

Does LM306D require external pull-up resistors on its output?

Yes, the LM306D features an open-collector output (pin 5), which means it can only sink current - it cannot source current. An external pull-up resistor to VCC+ (or another logic rail) is mandatory to establish a valid high-level output voltage. Typical values range from 1 kΩ to 10 kΩ depending on speed and load requirements; lower resistance improves rise time but increases power consumption when output is low.

Can LM306D operate with a single positive supply?

No, the LM306D is not designed for single-supply operation. Its internal architecture requires both a positive supply (VCC+, pin 8) and a negative supply (VCC−, pin 7) to bias the differential input stage and output transistor correctly. Attempting to tie VCC− to ground results in non-functional behavior - the device will not produce correct output transitions or meet specified offset and response time performance.

What is the function of the two strobe inputs on LM306D?

The STROBE 1 (pin 4) and STROBE 2 (pin 3) inputs on LM306D are active-low control terminals that override the comparator's normal operation: when either is pulled low, the output (pin 5) is forced high regardless of the IN+ and IN− voltages. This enables hardware-level blanking, synchronization, or fault masking - for example, disabling fault detection during power-up sequencing or muting comparator output during data acquisition windows.

Is LM306D pin-compatible with National Semiconductor's LM306?

Yes, the LM306D is a Texas Instruments second-source replacement for National Semiconductor's LM306 and maintains full pin-to-pin and functional compatibility in both SOIC (D) and PDIP (P) packages. Electrical specifications, timing behavior, thermal characteristics, and absolute maximum ratings match identically, allowing drop-in replacement in existing designs originally specifying the National Semiconductor part.