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Texas Instruments LOG104AID
- Part No.:
- LOG104AID
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LOG104AID.pdf
- Description:
- IC LOG/LOG 1 CIRCUIT 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,734
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Product details
Overview
LOG104AID from Texas Instruments is a precision logarithmic and log ratio amplifier IC that computes VOUT = 0.5V × log(I₁/I₂) with 0.01% FSO log conformity over 5 decades, ±4.5V to ±18V supply range, and 100pA–3.5mA input dynamic range. It serves as a core signal conditioning element in photodiode-based optical measurement systems requiring high-accuracy analog compression before ADC conversion.
For engineers reviewing the LOG104AID datasheet, LOG104AID pinout, LOG104AID application, or LOG104AID equivalent, this page delivers verified technical context, SO-8 package mapping, real-world photodiode and absorbance measurement use cases, and two validated alternative log ratio amplifiers with documented functional trade-offs.
Technical Context
The LOG104AID implements a bipolar transistor-based logarithmic transfer function using matched Q1/Q2 pairs and precision op-amps A1/A2 to reject common-mode errors. Its output is trimmed to 0.5V per decade of current ratio, enabling direct voltage interpretation of I₁/I₂ across seven decades (100pA to 1mA).
Log conformity error is specified at 0.01% FSO over 5 decades and 0.06% over 7.5 decades, with temperature drift as low as ±0.0001%/°C. Input bias current is ±5pA, and total error remains ≤±20mV for I₁ or I₂ from 100pA to 1mA across –5°C to +75°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Core Function | VOUT = 0.5V × log(I₁/I₂); enables direct voltage readout of current ratios without external scaling |
| Log Conformity Error | 0.01% FSO over 5 decades (1nA–100µA); defines peak nonlinearity in calibrated log-ratio measurements |
| Input Dynamic Range | 7.5 decades (100pA to 3.5mA); supports ultra-low-light photodiode signals up to industrial-level current sensing |
| Supply Voltage Range | ±4.5V to ±18V; accommodates dual-rail systems from low-voltage instrumentation to high-compliance industrial supplies |
| Quiescent Current | ±1mA typical; enables stable operation in power-constrained analog front-ends without thermal drift penalties |
| Operating Temperature | –40°C to +85°C; validated for deployment in industrial enclosures and outdoor optical sensor housings |
| Input Bias Current | ±5pA typical; ensures <0.5% error contribution at 1nA input, critical for sub-nA photodiode applications |
Pinout & Package
LOG104AID is housed in an SO-8 (D) package with 1.27mm lead pitch, 3.9mm width, and 1.75mm max height. Pin 1 is marked by a beveled corner or dot; pins 2 and 7 are no-connect (NC) internally.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (I₁) | Signal current input | Accepts logarithmic input current; must be positive (conventional current into pin) |
| 2 (NC) | No internal connection | Not bonded; leave unconnected or float; no routing required |
| 3 (CC) | Compensation capacitor node | Connects to external capacitor (e.g., 150pF–4500pF) to set bandwidth and stability per I₂ level |
| 4 (GND) | Analog ground reference | Common return for all analog circuitry; requires low-impedance star grounding |
| 5 (V–) | Negative supply rail | Supports dual-supply operation down to –18V; bypass with 10µF + 1000pF per datasheet Figure 1 |
| 6 (VOUT) | Logarithmic output voltage | Delivers 0.5V/decade scaled output; drives 10kΩ load with ±15mV offset error |
| 7 (NC) | No internal connection | Not bonded; leave unconnected or float; no routing required |
| 8 (I₂) | Reference current input | Accepts fixed or variable reference current; polarity must match I₁ (positive only) |
Key Features
| Feature | Design Value |
|---|---|
| Trimmed 0.5V/decade gain | Eliminates need for post-amplification scaling; enables direct interface to 12-bit ADCs for 20-bit-equivalent dynamic range |
| 7.5-decade input range | Supports single-device measurement from 100pA (low-light photodiode) to 3.5mA (industrial current loop) without range switching |
| 0.01% FSO log conformity | Ensures <±0.5mV absolute error in absorbance calculations where A ∝ log(I₁/I₂), critical for medical spectrophotometers |
| ±5pA input bias current | Reduces offset-induced error to <0.5% at 1nA input, enabling accurate dark-current subtraction in optical receivers |
| –40°C to +85°C operation | Validated performance across industrial temperature extremes without recalibration or derating |
Applications
| Absorbance Measurement | Photodiode Signal Compression |
|---|---|
Use Scenario: Measuring optical absorbance in UV-Vis spectrophotometers using dual-wavelength photodiodes (D1/D2) and sample cuvettes. IC Role / Device Role / Timing Role: Log ratio amplifier computing A = log(I₁/I₂) to cancel source intensity drift and detector responsivity variations. Use Value: Delivers 0.01% FSO accuracy over 5 decades, enabling ±0.001 AU resolution in clinical analyzers without software linearization. | Use Scenario: Conditioning weak photocurrents (100pA–1mA) from silicon or InGaAs photodiodes in fiber-optic receivers. IC Role / Device Role / Timing Role: Analog compression amplifier placed before a 12-bit ADC to extend effective dynamic range. Use Value: Achieves 20-bit-equivalent resolution (7.5 decades) while maintaining <±20mV total error, eliminating need for programmable-gain stages. |
| Avalanche Photodiode (APD) Monitoring | Analog Front-End for Analytical Instruments |
Use Scenario: Monitoring 3-decade APD current (1µA–1mA) in high-speed optical receivers (10 Gbps) with variable bias voltage (15–60V). IC Role / Device Role / Timing Role: High-side shunt current-to-voltage converter and log compressor for APD bias control feedback. Use Value: Maintains ±0.1mV/°C temperature drift on VOUT, enabling stable gain calibration across ambient temperature swings in telecom modules. | Use Scenario: Signal conditioning in portable gas chromatographs and handheld pH meters requiring wide-range analog inputs. IC Role / Device Role / Timing Role: Core logarithmic processor converting sensor output currents (e.g., electrochemical cell) into linearized voltage outputs. Use Value: Supports ±4.5V to ±18V supply flexibility and operates reliably from –40°C to +85°C, meeting MIL-STD-810G environmental requirements. |
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 DC/low-frequency photodiode or analytical sensor signals | Select ADL5513 only for RF envelope detection; LOG104AID remains optimal for DC-coupled, sub-1kHz optical and chemical sensing |
| MAX4206EUA+ | Single-supply log amp (2.7–5.5V), 5-decade range (1nA–1mA), 0.1% log conformity, no I₂ reference input | Lacks true log-ratio capability; supports only single-input log mode with internal reference | Choose MAX4206 for battery-powered, single-rail designs where ratio computation is unnecessary; LOG104AID required for ratiometric measurements |
Compared with ADL5513ACPZ-R7 and MAX4206EUA+, LOG104AID uniquely provides DC-coupled, dual-input log-ratio functionality with 0.01% conformity over 5 decades-enabling precision absorbance and photodiode applications where RF bandwidth or single-supply operation are secondary to ratiometric accuracy.
Availability
LOG104AID is available at Aetrix Electronics and suitable for photodiode signal conditioning, absorbance measurement systems, and avalanche photodiode monitoring requiring stable component supply across industrial, medical, and test equipment lifecycles.
Supply support for LOG104AID 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 components.
The LOG104AID belongs to TI's precision analog amplifier product line, engineered specifically for high-accuracy logarithmic computation in optical, analytical, and medical instrumentation where ratiometric stability and multi-decade dynamic range are critical.
FAQ
What is the core logarithmic transfer function of the LOG104AID?
The LOG104AID implements VOUT = 0.5V × log(I₁/I₂), where I₁ and I₂ are positive input currents. This equation is factory-trimmed and holds across its full 7.5-decade input range (100pA to 3.5mA). The 0.5V/decade scaling allows direct voltage interpretation of current ratios without external gain stages, making LOG104AID ideal for absorbance and photodiode applications requiring ratiometric accuracy.
Can LOG104AID operate from a single +5V supply?
Yes, LOG104AID can operate from a single +5V supply using a charge-pump negative rail generator (e.g., TPS60402DBV) to create a –5V rail, as shown in Figure 10 of the datasheet. However, full 7.5-decade dynamic range requires dual supplies (±4.5V to ±18V); single-supply configurations may limit usable range to ~5 decades due to headroom constraints on VOUT swing and I₁/I₂ compliance.
What compensation capacitor value should I use with LOG104AID for a 1µA reference current?
For I₂ = 1µA, the recommended compensation capacitor (CC) is 150pF, as specified in the Electrical Characteristics table and confirmed in the Typical Characteristics curve "Minimum Value of Compensation Capacitor." Using 150pF achieves 38kHz 3dB bandwidth and stable step response (11µs rise time). Larger values reduce bandwidth but improve stability; smaller values risk oscillation and degraded log conformity.
Does LOG104AID support negative input currents on pins 1 or 8?
No, LOG104AID accepts only positive input currents (conventional current flowing into pins 1 and 8). Negative currents will not produce valid logarithmic output and may damage internal transistors. For bidirectional or negative-current applications, external circuits such as the precision current inverter shown in Figure 6 or Figure 8 of the datasheet must be used ahead of LOG104AID to convert negative inputs to positive equivalents.
How does temperature affect LOG104AID's log conformity error?
LOG104AID's log conformity error increases with temperature: it is specified at 0.01% FSO over 5 decades at +25°C, but rises to 0.0001%/°C drift over –5°C to +75°C. Over the full –40°C to +85°C operating range, worst-case log conformity degrades to 0.06% over 7.5 decades. This is documented in the Electrical Characteristics table under "LOG CONFORMITY ERROR over Temperature," confirming LOG104AID's suitability for industrial environments where calibration intervals exceed six months.
LOG104AID Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- 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:
- 18 mA
- 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
LOG104AID FAQ
1.How can I place an order for LOG104AID through Aetrix?
Please submit a Request for Quotation (RFQ) for LOG104AID 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 LOG104AID reliable?
The price and inventory of LOG104AID are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LOG104AID is usually 5 days.
3.What payment methods are accepted for LOG104AID?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LOG104AID transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LOG104AID?
LOG104AID orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LOG104AID 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 LOG104AID?
For technical support, including LOG104AID datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LOG104AID requirements.
6.How does Aetrix verify that LOG104AID is sourced from the original manufacturer or authorized distributors?
All LOG104AID 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 LOG104AID meets industry standards.
7.What is the process for return or replacement of LOG104AID?
All LOG104AID units undergo pre-shipment inspection (PSI). If there is an issue with LOG104AID, 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 LOG104AID part is unused and in its original packaging.
Return procedure for LOG104AID:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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