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Texas Instruments LOG104AIDE4
- Part No.:
- LOG104AIDE4
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LOG104AIDE4.pdf
- Description:
- IC LOG/LOG 1 CIRCUIT 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,328
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Product details
Overview
LOG104AIDE4 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), operating from ±4.5V to ±18V supplies, used in photodiode signal compression and analog front-end signal conditioning for high-dynamic-range instrumentation.
For engineers reviewing the LOG104AIDE4 datasheet, LOG104AIDE4 pinout, LOG104AIDE4 application, or LOG104AIDE4 equivalent, key selection criteria include its verified 7.5-decade input dynamic range, 0.5V/decade gain trim, low 5pA input bias current, ±1.5mA quiescent supply current, and SOIC-8 package compatibility with industrial temperature operation (–40°C to +85°C).
Technical Context
The LOG104AIDE4 implements a true bipolar transistor-based logarithmic core using matched Q1/Q2 pairs and precision op-amps A1/A2 to realize the transfer function VOUT = 0.5V × log(I₁/I₂). Its architecture supports both absolute log and log-ratio modes, with internal trimming of scale factor and offset.
Input currents flow into pins 1 (I₁) and 8 (I₂); output appears at pin 6 (VOUT). Frequency compensation is externally set via capacitor CC between pins 3 and 8, with bandwidth ranging from 0.1kHz (at I₂ = 10nA) to 45kHz (at I₂ = 1mA), and transient response varies significantly between rising/falling edges due to nonlinear gain dependence on signal level.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Log Conformity Error | 0.01% FSO over 5 decades (1nA–100µA); ensures ≤0.5mV nonlinearity error in absorbance measurement systems |
| Input Dynamic Range | 7.5 decades (100pA to 3.5mA); enables single-device detection from ultra-low photodiode currents to high-level sensor outputs |
| Gain Accuracy | ±0.15% initial error, 0.01%/°C drift; maintains calibrated 0.5V/decade scaling across –40°C to +85°C operating range |
| Input Bias Current | ±5pA typ, doubles per 10°C; sets lower bound on usable input current (≤100pA degrades accuracy) |
| Supply Range | ±4.5V to ±18V; supports dual-rail operation in precision analog signal chains without external regulators |
| Output Offset | ±3mV initial, ±2µV/°C drift; allows system-level calibration to achieve sub-mV absolute output error |
| Total Error | ±20mV typical across 100pA–1mA inputs; defines worst-case deviation from ideal log transfer in data-compression applications |
Pinout & Package
LOG104AIDE4 is housed in an SOIC-8 (D) package, 3.9mm × 4.9mm body, 1.75mm max height, JEDEC MS-012 AA compliant, with gull-wing leads and RoHS-compliant NiPdAu finish (Level-3 MSL rating).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (I₁) | Signal current input | Conventional current flows into this pin; connects to photodiode cathode or transimpedance amplifier output |
| 2 (NC) | No internal connection | Unbonded die pad; must remain unconnected or grounded only if required by PCB layout for thermal/mechanical stability |
| 3 (CC) | Compensation capacitor node | Connects to pin 8 to set dominant pole; capacitor value selected per I₁/I₂ range (e.g., 150pF for µA-level signals) |
| 4 (GND) | Analog ground reference | Common return for internal amplifiers; requires low-impedance star grounding to minimize noise coupling |
| 5 (V⁻) | Negative supply rail | Accepts –4.5V to –18V; bypass with 10µF tantalum + 1000pF ceramic close to pin for PSRR optimization |
| 6 (VOUT) | Logarithmic output voltage | Delivers 0.5V per decade of I₁/I₂ ratio; drives 10kΩ load with ±15mV offset and <1.2mV/°C drift |
| 7 (NC) | No internal connection | Unbonded; no electrical function; may be left floating or tied to GND per board layout constraints |
| 8 (I₂) | Reference current input | Conventional current flows into this pin; typically driven by precision resistor or current source for log-ratio mode |
Key Features
| Feature | Design Value |
|---|---|
| 7.5-decade dynamic range | Supports single-amplifier measurement from 100pA (single-photon detector leakage) to 3.5mA (industrial sensor output) without range switching |
| 0.5V/decade gain trim | Enables direct interface to 12-bit ADCs: 7 decades ≈ 21-bit effective resolution, eliminating need for programmable-gain stages |
| Low 5pA input bias current | Minimizes loading error on high-impedance sources like photodiodes; allows use of >100MΩ feedback resistors in TIA front-ends |
| –40°C to +85°C operation | Validated performance across full industrial temperature range, with <0.0005%/°C log conformity drift enabling uncalibrated field deployment |
| External frequency compensation | Capacitor between pins 3 and 8 permits bandwidth optimization: 45kHz at 1mA vs. 0.1kHz at 10nA, matching signal slew requirements |
Applications
| Absorbance Measurement | Photodiode Signal Compression |
|---|---|
Use Scenario: Measuring optical absorbance in spectrophotometers using dual-wavelength photodiode pairs (D₁/D₂) to quantify sample concentration. IC Role / Device Role / Timing Role: Log-ratio amplifier computing A = log(I₁/I₂) with matched D₁/D₂ photocurrents, rejecting common-mode light-source drift. Use Value: Achieves <0.01% FSO accuracy over 5 decades, enabling sub-0.1% concentration resolution without digital post-processing. | Use Scenario: Compressing wide-dynamic-range photocurrents (e.g., from 100pA to 1mA) before digitization in medical pulse oximeters. IC Role / Device Role / Timing Role: Front-end analog compressor converting linear photocurrent to logarithmic voltage, preserving SNR across intensity extremes. Use Value: Delivers 7-decade input range → 21-bit effective ADC resolution using standard 12-bit converters, reducing BOM cost and power. |
| Analog Signal Conditioning for ADC | Avalanche Photodiode (APD) Current Monitoring |
Use Scenario: Preconditioning sensor outputs (e.g., gas sensors, radiation detectors) with >6-decade output spans prior to 12-bit SAR ADC sampling. IC Role / Device Role / Timing Role: High-accuracy logarithmic amplifier providing voltage output proportional to log(sensor current), linearizing exponential sensor responses. Use Value: Eliminates need for microcontroller-based lookup tables or floating-point math, enabling real-time linearized readings in resource-constrained embedded systems. | Use Scenario: Monitoring APD bias current across 3 decades (100nA–100µA) in fiber-optic receivers to maintain optimal avalanche gain. IC Role / Device Role / Timing Role: Precision current-to-voltage converter with logarithmic scaling, interfacing high-voltage APD bias circuits to low-voltage monitoring ADCs. Use Value: Enables stable APD gain control using simple voltage thresholds instead of complex current-sense amplifiers, improving receiver reliability. |
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, 3.3V single supply, 5ns response; no DC log-ratio capability | Designed for RF power measurement, not DC/low-frequency photodiode or sensor current processing | Select ADL5513 only for RF envelope detection; LOG104AIDE4 remains preferred for DC-coupled precision log-ratio tasks |
| LM13700N | OTA-based log amp, untrimmed gain, ±15V supply, 100pA–100µA range, no built-in compensation or offset trim | Requires external calibration and compensation networks; higher design effort for same accuracy | Choose LM13700N only for cost-sensitive, non-precision applications where ±5% log conformity is acceptable |
Compared with ADL5513ACPZ-R7 and LM13700N, LOG104AIDE4 uniquely delivers factory-trimmed 0.5V/decade gain, 7.5-decade DC dynamic range, and integrated log-ratio architecture-making it the only option for calibrated absorbance measurement and photodiode compression without external trimming circuitry.
Availability
LOG104AIDE4 is available at Aetrix Electronics and suitable for photodiode signal compression, absorbance measurement systems, and analog front-end signal conditioning requiring stable component supply across industrial temperature ranges and long production lifecycles.
Supply support for LOG104AIDE4 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 90 years of innovation in precision signal chain components.
The LOG104 product line was engineered for high-accuracy DC logarithmic computation in analytical instrumentation, medical diagnostics, and industrial sensing-where multi-decade dynamic range and temperature-stable scaling are critical.
FAQ
What is the maximum input current the LOG104AIDE4 can handle without damage?
The LOG104AIDE4 has an absolute maximum input current rating of ±10mA per input (pins 1 and 8), but sustained operation above 3.5mA degrades log conformity beyond specification. For reliable 0.06% FSO accuracy across 7.5 decades, input currents must stay within 100pA to 3.5mA. Exceeding 3.5mA increases nonlinearity and risks thermal stress on the internal logging transistors. The LOG104AIDE4 datasheet specifies total input current (I₁ + I₂) ≤ 4.5mA on ±5V supplies to maintain compliance.
How does the LOG104AIDE4 achieve its 0.01% log conformity over 5 decades?
The LOG104AIDE4 achieves 0.01% log conformity over 5 decades through factory trimming of the logarithmic core's scale factor and offset, combined with matched bipolar transistor pairs (Q1/Q2) operated under isothermal conditions. Its architecture minimizes errors from input bias current (5pA typ), voltage offset (±0.3mV), and temperature drift (0.0001%/°C), all validated across –5°C to +75°C. This precision enables applications like absorbance measurement where deviations from ideal log behavior directly impact concentration accuracy.
Can the LOG104AIDE4 operate from a single +5V supply?
Yes, the LOG104AIDE4 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. Direct single-supply operation is not supported because the internal op-amps (A1/A2) require dual rails to handle input currents referenced to ground. Without a negative supply, input current injection into pins 1 or 8 would violate common-mode voltage limits, causing saturation or inaccurate output. The LOG104AIDE4's specified operating range remains ±4.5V to ±18V.
What is the role of the compensation capacitor (CC) between pins 3 and 8 on the LOG104AIDE4?
The compensation capacitor (CC) between pins 3 and 8 sets the dominant pole of the LOG104AIDE4's closed-loop response, stabilizing the logarithmic core against oscillation. Its value is inversely related to input current magnitude: 150pF for µA-level signals (38kHz BW), 50pF for mA-level (45kHz), and 4500pF for nA-level (0.1kHz). Selecting CC based on the minimum I₁ and maximum I₂ in the application ensures stability while maximizing bandwidth. Values below 2pF are ineffective; larger values improve phase margin but reduce usable bandwidth.
Does the LOG104AIDE4 support negative input currents?
No, the LOG104AIDE4 accepts only positive input currents-conventional current must flow *into* pins 1 (I₁) and 8 (I₂). Negative currents (sinking) will forward-bias internal protection diodes and cause malfunction or damage. For applications requiring negative current handling, external inversion circuits are necessary, such as the precision current inverter shown in Figure 6 of the LOG104AIDE4 datasheet, which uses chopper-stabilized op-amps and matched resistors to convert sinking currents to sourcing equivalents compatible with the LOG104AIDE4 inputs.
LOG104AIDE4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-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:
- -
- -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
LOG104AIDE4 FAQ
1.How can I place an order for LOG104AIDE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for LOG104AIDE4 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 LOG104AIDE4 reliable?
The price and inventory of LOG104AIDE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LOG104AIDE4 is usually 5 days.
3.What payment methods are accepted for LOG104AIDE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LOG104AIDE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LOG104AIDE4?
LOG104AIDE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LOG104AIDE4 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 LOG104AIDE4?
For technical support, including LOG104AIDE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LOG104AIDE4 requirements.
6.How does Aetrix verify that LOG104AIDE4 is sourced from the original manufacturer or authorized distributors?
All LOG104AIDE4 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 LOG104AIDE4 meets industry standards.
7.What is the process for return or replacement of LOG104AIDE4?
All LOG104AIDE4 units undergo pre-shipment inspection (PSI). If there is an issue with LOG104AIDE4, 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 LOG104AIDE4 part is unused and in its original packaging.
Return procedure for LOG104AIDE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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