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Texas Instruments LOG104AIDRG4
- Part No.:
- LOG104AIDRG4
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LOG104AIDRG4.pdf
- Description:
- IC LOG/LOG 1 CIRCUIT 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,222
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Product details
Overview
LOG104AIDRG4 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 ±1mA quiescent current, and delivers calibrated 0.5V/decade scaling for photodiode signal compression and analog front-end dynamic range extension in optical instrumentation.
For engineers reviewing the LOG104AIDRG4 datasheet, LOG104AIDRG4 pinout, LOG104AIDRG4 application, or LOG104AIDRG4 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 parametric differences.
Technical Context
The LOG104AIDRG4 implements a true bipolar transistor-based logarithmic transfer function using matched Q1/Q2 pairs and precision op-amps A1/A2 to reject temperature-induced VBE drift. Its core computation relies on the fundamental relationship VOUT = 0.5V × log(I₁/I₂), trimmed at factory for 0.5V/decade gain and low offset.
Input stage FETs deliver ±5pA bias current (doubling per 10°C), enabling accurate sub-nA current measurement. Frequency compensation via external capacitor (CC) between pins 3 and 8 allows bandwidth tuning from 0.1kHz (I₂ = 10nA) to 45kHz (I₂ = 1mA), with asymmetric step response optimized for increasing/decreasing signal transients.
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 |
| Dynamic Range | 7.5 decades (100pA to 3.5mA); supports single-device detection of weak photodiode signals and high-current APD outputs |
| Output Scaling | 0.5V per decade; enables direct interfacing to 12-bit ADCs without gain staging, achieving effective 20-bit dynamic range |
| Supply Range | ±4.5V to ±18V; accommodates industrial sensor interfaces requiring wide headroom and rail-to-rail compliance |
| Input Bias Current | ±5pA typ; permits accurate low-current photodiode sensing down to 100pA with minimal offset contribution |
| Operating Temp | –40°C to +85°C; validated for embedded optical analyzers and medical diagnostics equipment deployed in uncontrolled environments |
| Quiescent Current | ±1mA max; reduces thermal load in multi-channel instrumentation racks and portable battery-powered devices |
Pinout & Package
LOG104AIDRG4 is housed in an SOIC-8 (D) package with 1.27mm lead pitch, 3.9mm body width, and 1.75mm max height. Pin 1 is marked by a beveled corner or dot; pin 2 is NC (no internal connection).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (I₁) | Signal current input | Accepts logarithmic input current (e.g., photodiode anode); must be positive conventional current into pin |
| 2 (NC) | No internal connection | Not bonded; leave unconnected; no routing or grounding required |
| 3 (GND) | Analog ground reference | Common return for I₁, I₂, and VOUT; requires low-impedance star connection to minimize noise coupling |
| 4 (V⁻) | Negative supply rail | Connects to negative supply (–4.5V to –18V); bypass with 10µF tantalum + 1000pF ceramic close to pin |
| 5 (I₂) | Reference current input | Accepts stable reference current (e.g., resistor-derived from precision voltage); polarity matches I₁ |
| 6 (VOUT) | Logarithmic output | Delivers 0.5V × log(I₁/I₂); drives 10kΩ loads; short-circuit protected to ±18mA |
| 7 (V⁺) | Positive supply rail | Connects to positive supply (+4.5V to +18V); bypass identically to V⁻ |
| 8 (CC) | Compensation capacitor node | Connects external capacitor (e.g., 150pF for 1µA I₂) to stabilize loop; value scales inversely with I₂ magnitude |
Key Features
| Feature | Design Value |
|---|---|
| Factory-trimmed 0.5V/decade gain | Eliminates system-level calibration for log ratio applications like absorbance spectroscopy (A = log(I₁/I₂)) |
| 7.5-decade input range (100pA–3.5mA) | Enables single-component detection of ultra-low photodiode currents and high-gain avalanche photodiode outputs |
| Low 5pA input bias current | Reduces measurement error below 100pA; critical for high-impedance optical sensor front-ends |
| Asymmetric transient response | Optimized 11µs rise (I₂: 1µA→1mA) and 45µs fall (1mA→1µA) times prevent settling errors in pulsed-light systems |
| ±1mA quiescent current | Minimizes self-heating drift in multi-channel log amp arrays used in lab-grade analytical instruments |
Applications
| Absorbance Spectroscopy | Photodiode Signal Compression |
|---|---|
Use Scenario: Measuring light attenuation through chemical samples using dual-wavelength photodiodes (D1, D2) in spectrophotometers. IC Role / Device Role / Timing Role: LOG104AIDRG4 computes log ratio VOUT = 0.5V × log(ID1/ID2) to directly output absorbance A ∝ VOUT. Use Value: Achieves 0.01% FSO accuracy over 5 decades, eliminating need for digital post-processing and enabling analog-domain quantification of optical density. | Use Scenario: Compressing wide-dynamic-range photocurrent from silicon or InGaAs photodiodes before digitization. IC Role / Device Role / Timing Role: LOG104AIDRG4 acts as analog-domain compressor, converting linear photocurrent (100pA–1mA) into logarithmic voltage (0–3.5V). Use Value: Extends effective resolution of 12-bit ADCs to 20-bit equivalent dynamic range, preserving SNR across 7.5 decades without oversampling. |
| Avalanche Photodiode (APD) Monitoring | Analog Front-End for Precision Instrumentation |
Use Scenario: Real-time monitoring of APD current in fiber-optic receivers (10Gbps+) where photocurrent spans 3 decades (1µA–1mA). IC Role / Device Role / Timing Role: LOG104AIDRG4 serves as high-speed log amplifier in APD bias control loop, feeding VOUT to DAC for closed-loop gain adjustment. Use Value: 45kHz bandwidth at 1mA I₂ enables sub-25µs response, supporting burst-mode optical power stabilization in telecom modules. | Use Scenario: Front-end signal conditioning in portable gas analyzers, pH meters, and environmental sensors requiring ultra-low current measurement. IC Role / Device Role / Timing Role: LOG104AIDRG4 functions as programmable log ratio engine, accepting I₁ from electrochemical sensor and I₂ from temperature-stable reference. Use Value: ±5pA input bias and –40°C to +85°C operation ensure <±20mV total error across industrial temperature ranges without recalibration. |
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 | DC–10GHz RF log detector; 45dB dynamic range; 50Ω input; no I₂ reference input | Designed for RF power measurement, not DC/low-frequency log ratio; lacks dual-current architecture | Select when measuring RF envelope power; avoid for photodiode or precision DC log ratio tasks |
| LT1073CS8#PBF | Switching regulator controller; no logarithmic function; 1.25V reference; 100kHz switching | Power management IC; incompatible core functionality; cannot compute log(I₁/I₂) | Not a functional alternative; included only as common mis-selection in BOM audits |
Compared with LOG104AIDRG4, ADL5513ACPZ-R7 offers RF bandwidth but sacrifices DC accuracy and dual-input log ratio capability, while LT1073CS8#PBF is a power controller with no logarithmic function-neither serves as a drop-in or functional replacement for precision optical or analytical instrumentation.
Availability
LOG104AIDRG4 is available at Aetrix Electronics and suitable for absorbance spectroscopy, photodiode signal compression, and avalanche photodiode monitoring requiring stable component supply, long-lifecycle support, and traceable RoHS-compliant sourcing.
Supply support for LOG104AIDRG4 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 optical and analytical instrumentation, delivering factory-trimmed logarithmic transfer functions to replace complex discrete log amp designs in spectrophotometers, medical analyzers, and environmental sensors.
FAQ
What is the maximum input current the LOG104AIDRG4 can handle without damage?
The LOG104AIDRG4 has an absolute maximum input current rating of ±10mA per input (I₁ or I₂), as specified in the Absolute Maximum Ratings table. However, to maintain specified accuracy and avoid increased nonlinearity, input currents should be limited to 100pA–3.5mA. Exceeding 3.5mA degrades log conformity, and sustained currents above ±10mA risk permanent damage due to excessive power dissipation in the internal logging transistors. Always verify I₁ + I₂ ≤ 4.5mA on ±5V supplies.
Can the LOG104AIDRG4 operate from a single +5V supply?
Yes, the LOG104AIDRG4 can operate from a single +5V supply using a charge-pump circuit such as the TPS60402DBV to generate a negative rail, as shown in Figure 10 of the datasheet. Direct single-supply operation is not supported-the device requires both positive and negative rails to bias its internal op-amps and bipolar transistors correctly. Without a negative supply, inputs and outputs will saturate, and the logarithmic function fails. The minimum total supply span remains ±4.5V (i.e., +4.5V/–4.5V or +5V/–0V with level-shifting).
What is the purpose of the compensation capacitor (CC) on pin 8 of the LOG104AIDRG4?
The compensation capacitor (CC) connected between pin 8 (CC) and pin 3 (GND) stabilizes the LOG104AIDRG4's internal feedback loop and sets bandwidth. Its value depends on the operating input current: 150pF for I₂ = 1µA, 50pF for I₂ = 1mA, and up to 4500pF for I₂ = 10nA. Larger CC values improve stability but reduce bandwidth; smaller values increase bandwidth but risk oscillation. The Minimum Value of Compensation Capacitor curve in the datasheet guides selection based on your I₁/I₂ min/max combination.
How does temperature affect the log conformity error of the LOG104AIDRG4?
Temperature increases log conformity error linearly: 0.0001%/°C over 1nA–100µA (5 decades) and 0.0005%/°C over 100pA–3.5mA (7.5 decades). At the full operating range (–40°C to +85°C), this contributes up to ±0.063% additional error beyond the initial 0.06% spec. The device's matched transistor pair and on-chip thermal tracking minimize drift, but system-level calibration at two temperatures is recommended for applications demanding <0.02% total error across wide ambient swings.
Is the LOG104AIDRG4 pin-compatible with other log amplifier ICs like the AD8304 or MAX4206?
No, the LOG104AIDRG4 is not pin-compatible with AD8304 or MAX4206. Its SOIC-8 pinout (I₁, NC, GND, V⁻, I₂, VOUT, V⁺, CC) differs fundamentally: AD8304 uses a 14-pin TSSOP with separate REF, OUT, and VPOS pins, while MAX4206 is an 8-pin SOIC but assigns pins to VIN, VOUT, VREF, and GND in non-matching positions. Substituting requires PCB redesign. Functional equivalence is also limited-AD8304 is a 100dB RF log amp, and MAX4206 is a 60dB DC log amp with different scaling (20mV/dB vs. 0.5V/decade).
LOG104AIDRG4 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
LOG104AIDRG4 FAQ
1.How can I place an order for LOG104AIDRG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for LOG104AIDRG4 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 LOG104AIDRG4 reliable?
The price and inventory of LOG104AIDRG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LOG104AIDRG4 is usually 5 days.
3.What payment methods are accepted for LOG104AIDRG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LOG104AIDRG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LOG104AIDRG4?
LOG104AIDRG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LOG104AIDRG4 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 LOG104AIDRG4?
For technical support, including LOG104AIDRG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LOG104AIDRG4 requirements.
6.How does Aetrix verify that LOG104AIDRG4 is sourced from the original manufacturer or authorized distributors?
All LOG104AIDRG4 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 LOG104AIDRG4 meets industry standards.
7.What is the process for return or replacement of LOG104AIDRG4?
All LOG104AIDRG4 units undergo pre-shipment inspection (PSI). If there is an issue with LOG104AIDRG4, 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 LOG104AIDRG4 part is unused and in its original packaging.
Return procedure for LOG104AIDRG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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