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Texas Instruments LOG102AID
- Part No.:
- LOG102AID
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LOG102AID.pdf
- Description:
- IC LOG/LOG 1 CIRCUIT 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,568
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Product details
Overview
LOG102AID from Texas Instruments is a precision logarithmic and log ratio amplifier IC that computes VLOG OUT = 1 V × log(I₁/I₂) over six decades (1 nA to 1 mA), with 0.15% full-scale total error, ±55 mV worst-case output error, and dual uncommitted op amps (A3/A4) for scaling or signal loss detection. It serves as the core analog front-end in optical power meters and absorbance measurement systems.
For engineers reviewing the LOG102AID datasheet, LOG102AID pinout, LOG102AID application, or LOG102AID equivalent, this page delivers verified technical context, SO-14 package mapping, real-world use-value per application, and two validated alternative parts - all grounded in TI's SBOS211A production data sheet.
Technical Context
The LOG102AID implements a true bipolar transistor-based logarithmic transfer function using matched Q1/Q2 base-emitter voltage relationships, internally temperature-compensated via a positive-TC resistor network to cancel kT/q drift. Its core log section delivers trimmed 1 V/decade output scaling with programmable gain (G = 1 + R₂/R₁) via external resistors on pins 4 and 7.
A3 and A4 are rail-to-rail input/output op amps (±4.5 V to ±18 V supply), each offering 1.4 MHz GBW, 0.5 V/µs slew rate, and ±750 µV max input offset - configured externally for output scaling, filtering, or photodiode signal loss detection via comparator action at VOUT4.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Log Function | VLOG OUT = 1 V × log(I₁/I₂); enables direct decade-based current ratio measurement without digital computation |
| Total Error (0°C to +70°C) | ±55 mV max at I₁ or I₂ = 1 mA; defines absolute output deviation from ideal log curve in production-critical instrumentation |
| Input Dynamic Range | 6 decades (1 nA to 1 mA); supports single-device measurement of photodiode currents from ultra-low-light to high-intensity optical signals |
| Log Conformity Error | 0.15% FSO over 6 decades; quantifies peak nonlinearity vs best-fit line - primary accuracy limit after system calibration |
| Quiescent Current | 1.25 mA typical; enables stable operation in ±5 V powered portable optical meters without excessive thermal load |
| Supply Voltage Range | ±4.5 V to ±18 V; allows flexible biasing in industrial test equipment with wide rail tolerances |
| Operating Temperature | –40°C to +85°C; supports deployment in field-deployable optical density analyzers and factory-floor instrumentation |
Pinout & Package
LOG102AID is housed in a 14-pin SOIC (SO-14) package with standard JEDEC MS-012 footprint (body width 3.90 mm, lead pitch 1.27 mm). Pin 1 is index-marked; pins 2, 13, and NC positions are not internally connected.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 14 | I₁, I₂ Input Terminals | Positive conventional current inputs for log ratio computation; require external current sources (e.g., photodiode + reference resistor) |
| 3, 4, 7, 10 | A3/A4 Inverting/Non-inverting Inputs & Outputs | Configurable op amp terminals: A3 (pins 3,4,7), A4 (pins 10,11,12); used for gain scaling (R₁/R₂), offset correction, or loss-detection comparator |
| 5, 14 | Compensation Capacitor Connection | CC between pins 5 and 14 sets bandwidth: 4500 pF for 10 nA I₂, 50 pF for 1 mA I₂ - critical for stability vs. signal level |
| 6, 9 | V⁺, V⁻ Power Rails | Split-supply inputs supporting ±4.5 V to ±18 V; require local 10 µF + 1000 pF bypassing per TI layout guidance |
| 8 | VLOG OUT | Main log ratio output: 1 V/decade, trimmed at wafer test; connects directly to ADC or A3/A4 for scaling |
| 2, 13 | NC | No internal connection - must remain unconnected per TI specification |
Key Features
| Feature | Design Value |
|---|---|
| Core Log Ratio Accuracy | 0.15% FSO total error over 6 decades ensures calibrated optical density readings without software linearization |
| Dual Uncommitted Op Amps | A3/A4 provide on-chip gain staging and loss detection - eliminates need for external op amps in compact photodiode front-ends |
| Temperature-Compensated Log Core | Internal kT/q drift cancellation maintains <0.002%/°C log conformity error across –40°C to +85°C operating range |
| Programmable Output Gain | G = 1 + R₂/R₁ scaling via external resistors enables direct match to 0–5 V or 0–10 V ADC input ranges |
| Low Input Bias Current | ±5 pA typical at A1/A2 inputs minimizes error when measuring sub-10 nA photodiode currents |
Applications
| Optical Power Metering | Absorbance Measurement |
|---|---|
Use Scenario: Measuring laser diode output power across 6 decades (–60 dBm to 0 dBm) in handheld field calibrators. IC Role / Device Role / Timing Role: LOG102AID acts as analog log ratio engine converting photodiode current to linear-in-dB voltage output. Use Value: Eliminates multi-range switching and digital correction - single IC achieves ±0.15 dB accuracy from 1 nA to 1 mA photocurrent. |
Use Scenario: Quantifying chemical concentration via UV-Vis spectrophotometer sample cell transmission (λ₁/λ₁′). IC Role / Device Role / Timing Role: LOG102AID computes A = log(I₁/I₂) where I₁ and I₂ are matched photodiode currents from reference and sample paths. Use Value: Delivers <0.01 AU resolution at 1.0 AU absorbance using only passive components and no microcontroller firmware. |
| Analog Signal Compression | Photodiode Front-End for A/D Conversion |
Use Scenario: Compressing 120 dB dynamic range sensor outputs (e.g., seismic accelerometers) before 12-bit ADC sampling. IC Role / Device Role / Timing Role: LOG102AID provides analog-domain compression with 1 V/decade slope, reducing required ADC bits. Use Value: Enables 12-bit ADC to resolve 20-bit-equivalent dynamic range - avoids costly high-resolution converters and oversampling. |
Use Scenario: Conditioning avalanche photodiode (APD) current (1 µA to 1 mA) in fiber-optic receiver modules. IC Role / Device Role / Timing Role: LOG102AID interfaces directly with APD anode/cathode, providing log-compressed voltage output to FPGA ADC. Use Value: Maintains 35 µs settling time for 3-decade APD current steps while rejecting common-mode noise via differential I₁/I₂ topology. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar logarithmic amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD8304ARUZ | Single-channel log amp; 5-decade range (100 pA to 100 µA); 2.5 V single supply; integrated temp sensor; no dual op amps | Better for low-power, battery-operated light meters; unsuitable for dual-current-ratio absorbance setups requiring I₁/I₂ topology | Select AD8304ARUZ when supply is single-ended and dynamic range ≤5 decades suffices; avoid when dual-op-amp signal conditioning is needed. |
| MAX4206EUA+ | Log ratio amp with 6-decade range (100 pA to 100 µA); ±5 V supply; includes internal 1.25 V reference; no uncommitted op amps | Designed for transimpedance + log compression in medical pulse oximetry; lacks A3/A4 flexibility for custom gain/loss detection | Select MAX4206EUA+ for medical-grade, calibrated log ratio with internal reference; choose LOG102AID when external op amp integration is required. |
Compared with AD8304ARUZ and MAX4206EUA+, LOG102AID uniquely combines 6-decade current ratio computation, dual configurable op amps, and split-supply operation - making it the only option among the three capable of self-contained photodiode signal loss detection and gain scaling in industrial optical analyzers.
Availability
LOG102AID is available at Aetrix Electronics and suitable for optical power metering, absorbance measurement, analog signal compression, photodiode front-end design, and precision current-ratio instrumentation requiring stable component supply across extended temperature ranges.
Supply support for LOG102AID 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 over 50 years of precision amplifier innovation and automotive-grade reliability validation.
The LOG102AID belongs to TI's precision analog logarithmic amplifier product line, engineered specifically for optical, analytical, and medical instrumentation demanding high-accuracy current-ratio computation without digital processing overhead.
FAQ
What is the guaranteed input current range for specified accuracy in LOG102AID?
The LOG102AID guarantees 0.15% full-scale total error only within the 1 nA to 1 mA input current range for either I₁ or I₂. Below 1 nA, input bias current (±5 pA) dominates error; above 1 mA, nonlinearity increases beyond spec. TI explicitly limits total I₁ + I₂ to 1.1 mA on ±5 V supplies to maintain compliance - exceeding this requires higher supply rails per SBOS211A Section "INPUT CURRENT RANGE".
How does LOG102AID achieve temperature-stable logarithmic performance?
LOG102AID uses matched bipolar transistors (Q1/Q2) whose base-emitter voltage (VBE) follows VBE = VT·ln(IC/IS). To cancel the inherent VT = kT/q temperature dependence, TI integrates a precision positive-temperature-coefficient resistor in the log core - confirmed by SBOS211A's "LOG CONFORMITY vs TEMPERATURE" plot showing only ±0.002%/°C drift over 6 decades.
Can LOG102AID accept voltage inputs directly, or must inputs be current-driven?
LOG102AID is optimized for current inputs (I₁, I₂) and requires them for full 6-decade accuracy. Voltage inputs are possible only via series resistors, but dynamic range collapses to ~3 decades due to input offset voltage (±1.5 mV) and voltage noise - as stated in SBOS211A "VOLTAGE INPUTS" section. For voltage-driven designs, external transimpedance amplifiers are mandatory before LOG102AID inputs.
What is the role of the compensation capacitor (CC) between pins 5 and 14 in LOG102AID?
The CC capacitor between pins 5 and 14 sets dominant-pole frequency compensation to stabilize the log core's nonlinear feedback loop. Its value depends strictly on I₂ magnitude: 4500 pF for 10 nA, 150 pF for 1 µA, and 50 pF for 1 mA (SBOS211A "FREQUENCY RESPONSE" table). Incorrect CC causes oscillation or slow settling - TI provides "MINIMUM VALUE OF COMPENSATION CAPACITOR" curves to select optimal values per application current levels.
Does LOG102AID support negative input currents on pins 1 or 14?
No - LOG102AID accepts only positive conventional current into pins 1 and 14 (I₁, I₂), as confirmed by SBOS211A "NEGATIVE INPUT CURRENTS" section. Attempting reverse current flow violates absolute maximum ratings and risks device damage. For bidirectional or negative-current applications, TI recommends external circuits like the current inverter in Figure 6 or Figure 8 - which use OPA2335 or LM394 to convert negative input to positive current fed into LOG102AID.
LOG102AID Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Amplifier Type:
- Logarithmic and Log Ratio
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 0.5V/µs
- Gain Bandwidth Product:
- 1.4 MHz
- -3db Bandwidth:
- 45 kHz
- Current - Input Bias:
- 5 pA
- Voltage - Input Offset:
- 300 µV
- Current - Supply:
- 1.25mA
- Current - Output / Channel:
- 18 mA
- Voltage - Supply Span (Min):
- 9 V
- Voltage - Supply Span (Max):
- 36 V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SOIC
LOG102AID FAQ
1.How can I place an order for LOG102AID through Aetrix?
Please submit a Request for Quotation (RFQ) for LOG102AID on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LOG102AID reliable?
The price and inventory of LOG102AID are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LOG102AID is usually 5 days.
3.What payment methods are accepted for LOG102AID?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LOG102AID transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LOG102AID?
LOG102AID orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LOG102AID order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LOG102AID?
For technical support, including LOG102AID datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LOG102AID requirements.
6.How does Aetrix verify that LOG102AID is sourced from the original manufacturer or authorized distributors?
All LOG102AID products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LOG102AID meets industry standards.
7.What is the process for return or replacement of LOG102AID?
All LOG102AID units undergo pre-shipment inspection (PSI). If there is an issue with LOG102AID, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LOG102AID part is unused and in its original packaging.
Return procedure for LOG102AID:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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