LT111A - 250ns Voltage Comparator | Analog Devices
MPN: LT111A ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
LT111A Overview
A voltage comparator is an integrated circuit that determines whether an input voltage is above or below a reference level, producing a logic output suitable for control, monitoring, or switching decisions. The LT111A belongs to the comparator family within analog integrated circuits and power-management control systems. Unlike an operational amplifier intended primarily for linear amplification, the comparator is optimized for fast, saturated output transitions and threshold decisions.
The LT111A improves on the LM111 general-purpose comparator according to the manufacturer datasheet. Its headline specifications include 1.0 mV maximum input offset voltage, 5.0 nA maximum input offset current, and 250 ns maximum response time. The input stage accepts differential input signals up to ±30 V, while the output can drive loads up to 50 mA referenced to ground or either supply, as stated in the datasheet search data.
The component includes offset balancing and strobe capability. A separate output ground pin allows the output reference to be selected independently of the circuit ground, which is useful when interfacing to systems with different output-return requirements. The output can also be combined for OR-style logic, although exact implementation depends on the surrounding circuit and output configuration.
Typical uses include precision threshold detection, sensor signal conditioning, window comparison, overvoltage indication, zero-crossing detection, and industrial control systems. The 250 ns response is suitable for systems that need faster decisions than general-purpose slow comparators while retaining wide input-voltage capability.
Designers must account for the obsolete lifecycle status, supply arrangement, input common-mode limits, output polarity, and thermal constraints. The verified manufacturer result identifies LT111A as obsolete and directs users to contact Analog Devices for a replacement product. New designs should therefore confirm availability, lifecycle status, and any recommended replacement before committing to production.
This page consolidates the verified manufacturer specifications, obsolete-status notice, package information, design guidance, and sourcing limitations for engineers comparing the LT111A with legacy comparator systems.
Drop-in alternatives for LT111A — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with LT111A (same form factor and footprint) — differing in Maximum Input Offset Current, Package, Product Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
No drop-in alternatives available for this product.
Request AlternativesLT111A Maximum Ratings & Electrical Characteristics
| Product Type | General-purpose voltage comparator |
| Maximum Input Offset Voltage | 1.0 mV |
| Maximum Input Offset Current | 5.0 nA |
| Maximum Response Time | 250 ns |
| Supply Configuration | Single 5 V to ±15 V |
| Differential Input Signal Range | ±30 V |
| Maximum Output Load Current | 50 mA referenced to ground or either supply |
| Output Ground | Separate output ground pin |
| Input Offset Balancing | Supported |
| Strobe Capability | Supported |
| Output OR Capability | Supported |
| Positive Input Voltage Limit | 30 V above negative supply |
| Negative Input Voltage Limit | Negative supply |
| Maximum Junction Temperature | 150 °C |
| Package | TO-5 |
LT111A to-5 Pin Configuration Guide
Pin configuration for LT111A (to-5 package). This analog component features input, output, and power supply pins. Refer to the manufacturer datasheet for offset null, compensation, and enable pin configurations. Ideal for signal conditioning and amplifier circuits.
No detailed pinout data available for LT111A.
Refer to the datasheet for full pin configuration.
Typical Applications
LT111A is suitable for 7 applications: Precision Threshold Detection, Sensor Signal Conditioning, Overvoltage and Fault Detection, Industrial Control Logic, Zero-Crossing Detection, Window and Limit Comparison, Legacy Test and Measurement.
Precision Threshold Detection
LT111A is suitable for threshold detection because the manufacturer specifies a maximum input offset voltage of 1.0 mV and a maximum response time of 250 ns. Place the sensed signal on one input and a reference voltage on the other, then use the output to trigger a control, alarm, or state transition. The comparison threshold can be affected by input offset, bias current, resistor tolerances, and supply variation, so the reference network should be evaluated rather than assumed ideal.
Recommended
Sensor Signal Conditioning
LT111A can convert a sensor-derived voltage into a clean logic decision when the sensor output crosses a defined limit. Its 5.0 nA maximum input offset current and 1.0 mV maximum input offset voltage provide defined starting points for input-stage design, while the 250 ns maximum response supports relatively prompt threshold events. Protection, filtering, input common-mode range, and grounding should be added around the sensor interface before deployment.
Recommended
Overvoltage and Fault Detection
The LT111A can monitor a power rail or control node and generate an overvoltage indication when the input exceeds a reference threshold. The separate output ground is useful when the comparator output must be referenced to a different return point, while the 250 ns maximum response can provide fast fault signaling. For safety-critical or high-energy systems, add independent filtering, appropriate resistor ratings, and a qualified replacement strategy because LT111A is obsolete.
Recommended
Industrial Control Logic
LT111A is applicable to industrial control logic when a comparator is needed to translate an analog condition into a switching command. Its single 5 V through ±15 V supply capability supports different supply arrangements, and the output can drive up to 50 mA loads referenced to ground or either supply. The obsolete lifecycle status requires lifecycle confirmation and a manufacturer-approved alternative before new production equipment is released.
Recommended
Zero-Crossing Detection
LT111A can be used to detect when an analog waveform crosses a reference level, with its 250 ns maximum response providing a defined propagation-time basis. The input stage accepts differential signals up to ±30 V according to the verified material, but external attenuation or protection may still be required. Check the selected supply, input voltage limits, output polarity, and external load before using the comparator in waveform or timing systems.
Recommended
Window and Limit Comparison
By combining threshold comparisons and logic functions, LT111A can support upper-limit, lower-limit, or window decisions. Its offset-balancing capability can help reduce threshold mismatch when appropriately connected, while the separate output ground provides flexibility in mixed-signal return paths. The circuit must be evaluated for logic overlap, noise margin, propagation delay, and the input and output limits specified by the manufacturer datasheet.
Recommended
Legacy Test and Measurement
LT111A is relevant to existing test and measurement equipment that uses a discrete general-purpose comparator for trigger, limit, or polarity decisions. The verified specifications provide useful references for repair and redesign: 1.0 mV maximum input offset voltage, 5.0 nA maximum input offset current, and 250 ns maximum response time. Because the product is obsolete, preserve the original datasheet and verify the exact replacement before changing calibrated equipment.
Recommended
Recommended Products Summary
Engineering reference data for LT111A — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | LT1011A | LM111 |
|---|---|---|---|
| Product Type | General-purpose voltage comparator | General-purpose comparator | General-purpose comparator |
| Package | TO-5 | TO-5 - verify exact package suffix | TO-5 - verify exact package suffix |
| Brand | Analog Devices | Analog Devices | Texas Instruments |
Key Differentiators
- Improved LM111 comparator positioning (vs LM111)
- Wide differential input capability (vs LM111)
- Separate output-ground flexibility (vs LT1011A)
Design Notes
Do not treat LT111A as a drop-in replacement solely because it is an LM111-family comparator. The verified material says LT111A is an improved version of the LM111, but it does not provide a complete pin and parameter equivalence table. Verify package suffix, pin functions, output architecture, input common-mode range, supply limits, propagation behavior, and output loading against the exact alternative datasheet before releasing a PCB or production order.
Keep comparator input traces short and away from high-current switching nodes because a 1.0 mV maximum input offset specification is only one contributor to real threshold accuracy. Place the threshold-setting components close to the input pins, use a low-value, low-noise reference path where appropriate, and provide a clean return for the separate output-ground pin. Ground-loop current can shift the decision point even when the comparator itself is operating correctly.
The LT111A supports single 5 V through ±15 V supplies according to the verified manufacturer data, but the external circuit must respect the positive and negative input limits. The positive input limit is 30 V above the negative supply, while the negative input limit is the negative supply. Confirm the complete operating condition, including output state and load, before applying external signals or connecting the output to another supply domain.
Compliance Information
The supplied manufacturer material identifies LT111A as obsolete but does not provide RoHS, REACH, lead-free, halogen-free, conflict-minerals, or AEC-Q100 status. Values remain unknown rather than inferred.
