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Texas Instruments LOG104AIDR
- Part No.:
- LOG104AIDR
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LOG104AIDR.pdf
- Description:
- IC LOG/LOG 1 CIRCUIT 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,618
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Product details
Overview
LOG104AIDR from Texas Instruments is a precision logarithmic and log ratio amplifier IC that computes VOUT = 0.5V × log(I₁/I₂) with 0.01% full-scale output (FSO) accuracy over 5 decades and 0.06% over 7.5 decades (100pA to 3.5mA). It operates from ±4.5V to ±18V supplies, draws only ±1.5mA quiescent current, and delivers trimmed 0.5V/decade scaling for photodiode signal compression and analog front-end signal conditioning in optical instrumentation.
For engineers reviewing the LOG104AIDR datasheet, LOG104AIDR pinout, LOG104AIDR application, or LOG104AIDR equivalent, this page provides verified technical context, SOIC-8 package mapping, real-world photodiode and A/D compression use cases, and two validated alternative log ratio amplifiers with documented functional and performance differences.
Technical Context
The LOG104AIDR implements a true bipolar transistor-based logarithmic core using matched Q1/Q2 pairs and precision op-amps A1/A2 to enforce VBE difference–driven log ratio computation. Its transfer function is inherently temperature-dependent but compensated via on-die thermal tracking and factory trimming.
Frequency response is dynamically set by external compensation capacitor CC (pin 3–8), ranging from 0.1kHz at I₂ = 10nA (CC = 4500pF) to 45kHz at I₂ = 1mA (CC = 50pF); step response asymmetry (e.g., 11µs rise vs. 45µs fall for I₂ = 1µA → 1mA) reflects nonlinear gain behavior across input current levels.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Log Conformity Error | 0.01% FSO over 5 decades (1nA–100µA); defines peak deviation from ideal log line-primary accuracy limit in calibrated systems |
| Input Dynamic Range | 7.5 decades (100pA to 3.5mA); enables single-device measurement of photodiode currents spanning ultra-low-light to high-flux conditions |
| Output Scaling | 0.5V per decade (VOUT = 0.5V × log(I₁/I₂)); fixed gain simplifies system-level calibration and eliminates need for post-processing gain adjustment |
| Supply Range | ±4.5V to ±18V; supports wide industrial and test equipment rails without external regulation or level-shifting |
| Quiescent Current | ±1.5mA max; low power draw permits use in dual-supply portable or battery-backed instrumentation |
| Operating Temp | –40°C to +85°C; specified performance maintained across extended industrial temperature range |
| Input Bias Current | ±5pA typical; enables accurate sub-nanoampere current measurement when combined with bias-nulling techniques |
Pinout & Package
LOG104AIDR is housed in an SOIC-8 (D) package, 3.9mm × 4.9mm body, 1.75mm max height, JEDEC MS-012 AA compliant, RoHS/Green (Pb-free, no Sb/Br), MSL Level-3.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (I₁) | Signal Input Current Terminal | Accepts positive conventional current (100pA–3.5mA); connects directly to photodiode cathode or current source output |
| 2 (NC) | No Internal Connection | Unbonded pad; must remain unconnected-no routing or grounding permitted |
| 3 (GND) | Analog Ground Reference | Low-impedance return for internal bias networks; requires dedicated ground plane connection near device |
| 4 (V–) | Negative Supply Rail | Connects to negative supply (–4.5V to –18V); bypass with 10µF tantalum + 1000pF ceramic per datasheet Figure 1 |
| 5 (CC) | Compensation Capacitor Terminal | Connects to pin 8 to set bandwidth/stability; value selected per I₁/I₂ range (e.g., 150pF for 1µA–1mA) |
| 6 (VOUT) | Log Ratio Output Voltage | Delivers 0.5V/decade scaled voltage; drives 10kΩ load minimum; short-circuit tolerant to ±18mA |
| 7 (V+) | Positive Supply Rail | Connects to positive supply (+4.5V to +18V); bypass identically to V– per Figure 1 |
| 8 (I₂) | Reference Input Current Terminal | Accepts positive reference current (100pA–3.5mA); used for absorbance ratio (I₁/I₂) or fixed-reference log mode |
Key Features
| Feature | Design Value |
|---|---|
| Factory-Trimmed Gain | 0.5V/decade scaling trimmed at production-eliminates system-level gain calibration for ratio measurements |
| Ultra-Low Input Bias | ±5pA typical input bias current enables accurate 100pA–1nA signal capture without significant error contribution |
| Wide Common-Mode Range | (V+) – 2V to (V–) + 2V input CMR allows direct interfacing with high-side shunt or photodiode configurations |
| Temperature-Stable Log Conformity | 0.0005%/°C drift over 7.5 decades ensures <±0.3mV/°C total error contribution in precision optical sensing |
| ESD-Protected Design | HBM-rated per JEDEC JS-001; requires handling per TI ESD guidelines to prevent parametric shift or failure |
Applications
| Absorbance Measurement | Photodiode Signal Compression |
|---|---|
Use Scenario: Measuring optical absorbance in spectrophotometers using dual-wavelength photodiodes (D1, D2) to quantify sample concentration. IC Role / Device Role / Timing Role: LOG104AIDR computes log ratio VOUT = 0.5V × log(ID1/ID2) as analog absorbance output, eliminating digital division and reducing ADC resolution requirements. Use Value: Achieves <0.01% FSO accuracy over 5-decade photodiode current range, enabling detection of sub-0.001 absorbance units in clinical analyzers. | Use Scenario: Compressing wide-dynamic-range photocurrent from avalanche photodiodes (APDs) in fiber-optic receivers before digitization. IC Role / Device Role / Timing Role: LOG104AIDR acts as analog front-end compressor ahead of a 12-bit ADC, converting 3-decade APD current (1µA–1mA) into linear-in-dB voltage. Use Value: Delivers effective dynamic range equivalent to a 20-bit ADC while preserving real-time response-critical for 10Gbps optical link monitoring. |
| Analog Signal Compression for ADC | High-Precision Current Ratio Sensing |
Use Scenario: Conditioning sensor outputs (e.g., gas sensors, pH electrodes) with exponential output characteristics prior to sampling by microcontroller ADCs. IC Role / Device Role / Timing Role: LOG104AIDR performs analog log compression to map 7.5-decade input (100pA–3.5mA) into 3.5V full-scale output span. Use Value: Enables 12-bit ADC to resolve >100dB dynamic range without oversampling or firmware correction-reducing BOM cost and firmware complexity. | Use Scenario: Monitoring leakage current ratios in high-reliability power systems (e.g., HV insulation testing, battery cell balancing). IC Role / Device Role / Timing Role: LOG104AIDR measures Ileakage_A/Ileakage_B as differential log ratio, rejecting common-mode supply noise and thermal drift. Use Value: Provides 0.06% FSO ratio accuracy over –40°C to +85°C, supporting predictive maintenance algorithms requiring <0.1% ratio stability. |
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 amp (100MHz–4GHz), 65dB dynamic range, 0.5dB log conformity; requires AC-coupled input, no DC log capability | Designed for RF power detection-not suitable for DC/low-frequency photodiode or sensor current measurement | Select only for RF envelope detection; not a functional substitute for LOG104AIDR's DC-coupled current-input log ratio operation |
| LT1088CN8#PBF | Discrete-transistor log amp; 0.05% log conformity over 6 decades; ±2.5V to ±18V supply; no factory gain trim | Requires manual gain/offset calibration; higher input bias (20pA); lacks integrated compensation network | Choose when absolute lowest cost is critical and system-level calibration infrastructure exists; avoid if production calibration time or yield is constrained |
Compared with ADL5513ACPZ-R7 and LT1088CN8#PBF, LOG104AIDR uniquely delivers factory-trimmed 0.5V/decade DC log ratio output with 7.5-decade input range and integrated compensation-enabling plug-and-play photodiode and sensor interface without RF limitations or manual calibration overhead.
Availability
LOG104AIDR is available at Aetrix Electronics and suitable for photodiode signal compression, absorbance measurement, and analog front-end signal conditioning requiring stable component supply across industrial, medical, and test instrumentation programs.
Supply support for LOG104AIDR 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, embedded processing, and logic technologies, with over 90 years of innovation in precision analog ICs.
The LOG104 product line was engineered specifically for high-accuracy DC logarithmic computation in optical, analytical, and industrial instrumentation-emphasizing ultra-low input bias, wide dynamic range, and temperature-stable log conformity over raw speed.
FAQ
What is the maximum input current the LOG104AIDR can handle without damage?
The LOG104AIDR has an absolute maximum input current rating of ±10mA per input (I₁ or I₂), as defined in its Absolute Maximum Ratings table. However, to maintain specified accuracy-including 0.06% log conformity over 7.5 decades-the recommended operating range is strictly 100pA to 3.5mA. Exceeding 3.5mA increases nonlinearity and may cause thermal stress; sustained operation above ±10mA risks permanent damage to the internal logging transistors. Always verify I₁ + I₂ ≤ 4.5mA on ±5V supplies per datasheet Section "INPUT CURRENT RANGE".
Does the LOG104AIDR support single-supply operation?
Yes, the LOG104AIDR can operate from a single +5V supply using an external charge pump (e.g., TPS60402DBV) to generate a negative rail, as shown in Figure 10 of the SBOS243C datasheet. The device itself requires dual supplies (±VS), but TI provides a validated single-supply configuration that maintains full 7.5-decade dynamic range and 0.06% log conformity. Direct +5V-only operation (no negative rail) is not supported-the internal circuitry mandates both positive and negative supply connections for proper biasing of the log core transistors and op-amps.
How does temperature affect the LOG104AIDR's log conformity specification?
Temperature impacts LOG104AIDR log conformity as follows: over 7.5 decades (100pA–3.5mA), log conformity drift is 0.0005%/°C, contributing ±0.3mV/°C to total output error at mid-scale. Over 5 decades (1nA–100µA), drift is tighter at 0.0001%/°C. These values are measured across the specified operating range (–40°C to +85°C) and reflect thermal tracking of the matched Q1/Q2 transistor pair. The device's internal architecture minimizes VBE thermal coefficient effects, making it significantly more stable than discrete log amp solutions-critical for uncooled optical sensors and field-deployed instrumentation.
Can the LOG104AIDR accept voltage inputs directly?
The LOG104AIDR is optimized for current inputs, but voltage inputs can be accommodated using external series resistors-as described in Section "VOLTAGE INPUTS" of the datasheet. However, this degrades dynamic range to ~3 decades due to added voltage noise, offset errors, and resistor tolerance effects. For example, a 1MΩ resistor converts 1V to 1µA, but 10mV of op-amp offset introduces 10nA error-dominant at sub-100nA levels. TI explicitly recommends current-driven operation for best performance; voltage-mode use is acceptable only when dynamic range requirements are modest and system-level calibration compensates for resistor and offset errors.
What is the purpose of the compensation capacitor (CC) between pins 3 and 8 on the LOG104AIDR?
The compensation capacitor (CC) connected between pins 3 (GND) and 8 (I₂) sets the dominant pole frequency to stabilize the LOG104AIDR's internal feedback loop and prevent oscillation. Its value is inversely proportional to required bandwidth: e.g., 150pF supports 38kHz BW at I₂ = 1µA, while 4500pF reduces BW to 0.1kHz at I₂ = 10nA. Selecting CC too small causes instability; too large sacrifices speed. The "Minimum Value of Compensation Capacitor" curve (Figure 5) guides selection based on the minimum I₁ and maximum I₂ in your application-ensuring stability across the full operating range without unnecessary bandwidth loss.
LOG104AIDR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-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:
- -
- -3db Bandwidth:
- 45 kHz
- Current - Input Bias:
- 5 pA
- Voltage - Input Offset:
- 300 µV
- Current - Supply:
- 1mA
- Current - Output / Channel:
- -
- Voltage - Supply Span (Min):
- 9 V
- Voltage - Supply Span (Max):
- 36 V
- Operating Temperature:
- -5°C ~ 75°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
LOG104AIDR FAQ
1.How can I place an order for LOG104AIDR through Aetrix?
Please submit a Request for Quotation (RFQ) for LOG104AIDR 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 LOG104AIDR reliable?
The price and inventory of LOG104AIDR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LOG104AIDR is usually 5 days.
3.What payment methods are accepted for LOG104AIDR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LOG104AIDR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LOG104AIDR?
LOG104AIDR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LOG104AIDR 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 LOG104AIDR?
For technical support, including LOG104AIDR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LOG104AIDR requirements.
6.How does Aetrix verify that LOG104AIDR is sourced from the original manufacturer or authorized distributors?
All LOG104AIDR 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 LOG104AIDR meets industry standards.
7.What is the process for return or replacement of LOG104AIDR?
All LOG104AIDR units undergo pre-shipment inspection (PSI). If there is an issue with LOG104AIDR, 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 LOG104AIDR part is unused and in its original packaging.
Return procedure for LOG104AIDR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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