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Texas Instruments LOG102AIDR
- Part No.:
- LOG102AIDR
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LOG102AIDR.pdf
- Description:
- IC LOG/LOG 1 CIRCUIT 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,441
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Product details
Overview
LOG102AIDR from Texas Instruments is a precision logarithmic and log ratio amplifier IC that computes the base-10 logarithm of the ratio of two input currents (I₁/I₂) with 0.15% full-scale output (FSO) total error over six decades (1 nA to 1 mA). It integrates two uncommitted op amps (A3, A4) for scaling, signal loss indication, or filtering, and delivers a trimmed output of 1 V per decade at VLOG OUT. It is used in optical power meters, absorbance measurement systems, and front-end analog signal compression before ADCs.
For engineers reviewing the LOG102AIDR datasheet, LOG102AIDR pinout, LOG102AIDR application, or LOG102AIDR equivalent, key selection criteria include its 6-decade dynamic range, ±4.5 V to ±18 V dual-supply operation, SO-14 package compatibility, and verified log conformity error of 0.15% over temperature - all critical for photodiode current compression and high-accuracy ratio metrology.
Technical Context
The LOG102AIDR implements a true logarithmic transfer function using matched bipolar transistor pairs with internal temperature compensation for VT = kT/q, enabling stable log ratio computation across –40°C to +85°C. Its core log section (A1/A2) operates on current inputs only, with input bias currents as low as ±5 pA and offset voltage ≤±0.3 mV.
A3 and A4 are rail-to-rail output op amps with 1.4 MHz gain-bandwidth product, 0.5 V/µs slew rate, and ±750 µV max input offset voltage - configured externally for gain scaling (e.g., G = 1 + R₂/R₁), level shifting, or comparator-based signal loss detection at VOUT3/VOUT4.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Log Function | VLOG OUT = 1 V × log₁₀(I₁/I₂); enables direct decade-based scaling without external calibration |
| Dynamic Range | 6 decades (1 nA to 1 mA); supports photodiode signals from ultra-low-light to high-intensity optical sensing |
| Total Error | ±0.15% FSO over 6 decades; ensures <±37 mV absolute error at 1 nA input, critical for absorbance accuracy |
| Supply Range | ±4.5 V to ±18 V; allows flexible biasing in industrial and test equipment with wide supply margins |
| Quiescent Current | 1.25 mA typical; enables low-power operation in battery-backed optical instrumentation |
| Operating Temp | –40°C to +85°C; validated performance across automotive and industrial ambient conditions |
| Package | SO-14 (D package); surface-mount compatible with standard reflow profiles and IPC-compliant layout |
Pinout & Package
LOG102AIDR is housed in a 14-pin SOIC (Small Outline Integrated Circuit) package, designated D by Texas Instruments, with 1.27 mm lead pitch and JEDEC MS-012 compliance. Thermal resistance θJA is 100°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 14 | I₁, I₂ Input Terminals | Positive current inputs for log ratio computation; require conventional current flow into pins |
| 3, 4, 7, 8 | A3/A4 Op Amp Terminals | +IN3/–IN3/+IN4/–IN4; configurable for gain scaling, offset correction, or loss-detection comparator |
| 5, 12 | VLOG OUT / VOUT3 | Main log output (1 V/decade) and scaled output via A3; both rail-to-rail capable |
| 6, 9 | V⁺ / V⁻ | Dual supply rails; bypassing with 10 µF + 1000 pF capacitors per rail required for noise immunity |
| 10, 11 | VOUT4 / GND | Secondary op amp output and ground reference; GND must be low-impedance for log accuracy |
| 2, 13 | NC | No internal connection; must remain unconnected per datasheet to avoid parasitic coupling |
Key Features
| Feature | Design Value |
|---|---|
| Trimmed 1 V/decade output | Eliminates need for external DAC or digital calibration in optical density measurement systems |
| Two uncommitted op amps | Enables integrated signal conditioning - e.g., A4 as loss-of-signal comparator without added components |
| Low 5 pA input bias current | Preserves accuracy down to 1 nA input; avoids significant error in photodiode applications with high-impedance sources |
| Internal VT temperature compensation | Maintains log conformity stability over –40°C to +85°C without external thermistors or calibration tables |
| Compensation capacitor interface (Pin 5–14) | Allows bandwidth optimization: CC = 150 pF for 1 µA–1 mA inputs yields 38–45 kHz 3dB response |
Applications
| Optical Power Metering | Absorbance Measurement |
|---|---|
|
Use Scenario: Measuring optical power from fiber-optic transceivers or laser diodes across >60 dB dynamic range. IC Role / Device Role / Timing Role: LOG102AIDR serves as the core log ratio amplifier converting photodiode current to linear-in-dB voltage. Use Value: Delivers 0.15% FSO error at 1 nA–1 mA, enabling accurate +/–0.01 dB resolution in telecom power monitoring. |
Use Scenario: Quantifying light absorption through chemical samples in spectrophotometers. IC Role / Device Role / Timing Role: Computes A = log(I₁/I₂) between reference and sample path photodiodes. Use Value: Internal temperature-compensated log conformity eliminates drift-induced calibration errors in lab-grade instruments. |
| Analog Signal Compression | Front-End for High-Resolution ADC |
|
Use Scenario: Compressing wide-dynamic-range sensor outputs (e.g., radiation detectors, pressure transducers) prior to digitization. IC Role / Device Role / Timing Role: LOG102AIDR provides logarithmic compression to extend effective ADC resolution. Use Value: 6-decade input range maps to ~6 V output span, converting a 12-bit ADC into ~20-bit-equivalent dynamic range. |
Use Scenario: Interfacing avalanche photodiode (APD) current (1 µA–1 mA) to 12-bit SAR ADCs in medical imaging. IC Role / Device Role / Timing Role: LOG102AIDR acts as precision current-to-voltage log converter with rail-to-rail output drive. Use Value: 1.25 mA quiescent current and SO-14 footprint enable compact, low-power front-end designs meeting IEC 60601 safety margins. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar logarithmic amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ADL5513ACPZ-R7 | RF log detector (100 MHz–4 GHz), 45 dB range, no dual op amps; requires external scaling circuitry | Designed for RF power measurement, not DC/low-frequency photodiode current ratios | Select when measuring RF envelope power; not suitable for optical absorbance or DC log ratio tasks |
| MAX4206EUA+ | Single-channel log amp, 7-decade range (100 pA–100 µA), no integrated op amps, ±2.5 V supply only | Limited to lower-current photodiode applications; lacks output amplification capability | Choose for ultra-low-current (<100 nA) sensing where LOG102AIDR's 1 nA floor is insufficient |
Compared with ADL5513ACPZ-R7 and MAX4206EUA+, LOG102AIDR uniquely combines 6-decade DC current log ratio computation, dual configurable op amps, and 1 V/decade trimmed output - making it irreplaceable for optical density, photodiode compression, and precision analog front-ends requiring integrated signal conditioning.
Availability
LOG102AIDR is available at Aetrix Electronics and suitable for optical power metering, absorbance spectroscopy, analog signal compression, and front-end ADC interfacing requiring stable component supply across industrial, test & measurement, and medical OEM programs.
Supply support for LOG102AIDR 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 innovation in precision signal chain solutions.
The LOG102AIDR belongs to TI's precision analog amplifier portfolio, designed specifically for high-accuracy logarithmic computation in optical, analytical, and instrumentation applications where wide dynamic range and temperature-stable ratio measurement are essential.
FAQ
What is the primary function of the LOG102AIDR?
The LOG102AIDR is a precision logarithmic ratio amplifier that computes VLOG OUT = 1 V × log₁₀(I₁/I₂) with 0.15% full-scale error over six decades (1 nA to 1 mA). It uses matched bipolar transistors with internal temperature compensation to maintain accuracy from –40°C to +85°C. The LOG102AIDR also integrates two uncommitted op amps (A3, A4) for output scaling, offset adjustment, or signal loss detection - making it a complete analog front-end for photodiode and optical sensing applications.
Can the LOG102AIDR accept voltage inputs directly?
No - the LOG102AIDR is optimized for current-mode operation. Voltage inputs require external series resistors to convert to current, but this limits dynamic range to ~3 decades due to input offset voltage and noise effects. The LOG102AIDR datasheet explicitly states "best performance with current inputs" and warns that voltage-driven configurations degrade log conformity and increase total error. For pure voltage-log applications, alternative architectures like dedicated voltage-input log amps should be evaluated - the LOG102AIDR must be used with I₁ and I₂ sourced as currents.
What is the role of the compensation capacitor (CC) in the LOG102AIDR?
The compensation capacitor (CC), connected between Pin 5 and Pin 14, stabilizes the LOG102AIDR's internal feedback loop and sets bandwidth. Its value depends on the minimum I₁ and maximum I₂ in the application: CC = 150 pF supports 38–45 kHz 3dB bandwidth for 1 µA–1 mA inputs, while 4500 pF reduces bandwidth to 0.1 kHz for 10 nA inputs. Using too small a CC causes instability and overshoot; too large a CC unnecessarily sacrifices speed. The LOG102AIDR's Typical Characteristics graph "Minimum Value of Compensation Capacitor" provides exact CC selection guidance per operating current range.
How does the LOG102AIDR handle negative input currents?
The LOG102AIDR accepts only positive conventional current flow into Pins 1 and 14 (I₁, I₂). Negative currents are not supported internally. To process inverted or bidirectional signals, external circuits are required - such as the precision current inverter shown in Figure 7 of the LOG102AIDR datasheet, which uses matched op amps and transistors to generate a proportional positive current. Attempting to force negative current into LOG102AIDR pins violates Absolute Maximum Ratings and may cause permanent damage or unpredictable output behavior.
What are the supply voltage requirements for the LOG102AIDR?
The LOG102AIDR operates on dual supplies from ±4.5 V to ±18 V, with typical characterization at ±5 V. Supply rejection is specified at ±5 µV/V for the core log section and ±10 µV/V for A3/A4 op amps. Each supply rail must be bypassed with a 10 µF tantalum capacitor in parallel with a 1000 pF ceramic capacitor, placed as close as possible to Pins 6 (V⁺) and 9 (V⁻). Failure to implement proper bypassing increases noise susceptibility and degrades log conformity - especially critical in low-current (≤100 nA) applications where supply ripple couples directly into the logging transistors.
LOG102AIDR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- -
- 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
LOG102AIDR FAQ
1.How can I place an order for LOG102AIDR through Aetrix?
Please submit a Request for Quotation (RFQ) for LOG102AIDR 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 LOG102AIDR reliable?
The price and inventory of LOG102AIDR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LOG102AIDR is usually 5 days.
3.What payment methods are accepted for LOG102AIDR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LOG102AIDR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LOG102AIDR?
LOG102AIDR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LOG102AIDR 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 LOG102AIDR?
For technical support, including LOG102AIDR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LOG102AIDR requirements.
6.How does Aetrix verify that LOG102AIDR is sourced from the original manufacturer or authorized distributors?
All LOG102AIDR 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 LOG102AIDR meets industry standards.
7.What is the process for return or replacement of LOG102AIDR?
All LOG102AIDR units undergo pre-shipment inspection (PSI). If there is an issue with LOG102AIDR, 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 LOG102AIDR part is unused and in its original packaging.
Return procedure for LOG102AIDR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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