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Texas Instruments LOG101AID
- Part No.:
- LOG101AID
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LOG101AID.pdf
- Description:
- IC LOG/LOG 1 CIRCUIT 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:729
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Product details
Overview
LOG101AID from Texas Instruments is a precision logarithmic and log ratio amplifier IC that computes VOUT = 1V × log(I₁/I₂) using matched bipolar transistor core architecture. It delivers 0.01% FSO log conformity over 5 decades (1nA–100µA), supports ±4.5V to ±18V dual supplies, and operates across –40°C to +85°C. It is used in photodiode signal compression, absorbance measurement, and front-end analog signal compression for A/D converters.
For engineers reviewing the LOG101AID datasheet, LOG101AID pinout, LOG101AID application, or LOG101AID equivalent, this page provides verified technical context, SO-8 package mapping, real-world design meaning of key specs (e.g., 1V/decade gain, 7.5-decade input range), and two validated alternative parts with documented functional and application differences.
Technical Context
The LOG101AID implements a true logarithmic transfer function via temperature-compensated bipolar junction transistor pairs (Q1/Q2) and precision op-amps (A1/A2), eliminating need for external trimming. Its internal compensation network (CC pin 3–8) enables bandwidth tuning from 0.1kHz to 45kHz depending on I₂ level and capacitor value.
It operates exclusively with positive current inputs into pins 1 (I₁) and 8 (I₂); negative currents require external inversion circuits. Input bias current is ±5pA (typ), doubling every 10°C, and total input current (I₁ + I₂) must remain ≤4.5mA on ±5V supplies to maintain compliance and accuracy.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Core Function | VOUT = 1V × log(I₁/I₂); enables direct decade-based scaling of photodiode or sensor current ratios without digital computation. |
| Log Conformity Error | 0.01% FSO over 5 decades (1nA–100µA); ensures <±0.2mV deviation from ideal log line at 25°C, critical for high-fidelity optical absorbance systems. |
| Input Dynamic Range | 7.5 decades (100pA to 3.5mA); supports ultra-low-light photodiode signals up to industrial-level current sensing without range switching. |
| Supply Range | ±4.5V to ±18V; allows operation from low-voltage lab instrumentation to high-compliance industrial power rails. |
| Quiescent Current | ±1mA (typ); enables stable performance in power-constrained analog front-ends while maintaining full dynamic accuracy. |
| Operating Temp | –40°C to +85°C; validated for deployment in automotive cabin sensors, industrial analyzers, and field-deployed test equipment. |
| Gain Accuracy | ±0.15% (typ) over 1nA–100µA; guarantees consistent 1V/decade scaling across production units without per-device calibration. |
Pinout & Package
LOG101AID is housed in an SOIC-8 (D) package, 3.9mm × 4.9mm, 1.75mm max height, RoHS-compliant NIPDAU finish, MSL Level-3 (260°C peak reflow).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (I₁) | Signal current input | Positive input for variable current (e.g., photodiode anode); must be ≥100pA for specified accuracy; no internal connection to ground or supply. |
| 2 (NC) | No internal connection | Unbonded pad; must remain unconnected-no routing, pull-up, or bypassing permitted. |
| 3 (GND) | Analog ground reference | Common return for internal amplifiers; requires low-impedance star grounding to minimize offset drift and noise coupling. |
| 4 (V–) | Negative supply rail | Connects to negative supply (–4.5V to –18V); bypass with 10µF tantalum + 1000pF ceramic close to pin for stability. |
| 5 (NC) | No internal connection | Unbonded pad; electrically isolated-must not be tied to any net. |
| 6 (VOUT) | Logarithmic output | Provides voltage proportional to log(I₁/I₂); drives 10kΩ load minimum; short-circuit tolerant up to ±18mA. |
| 7 (V+) | Positive supply rail | Connects to positive supply (+4.5V to +18V); same bypassing requirement as V– for noise immunity. |
| 8 (I₂) | Reference current input | Positive input for fixed reference current (e.g., resistor-derived or precision current source); sets denominator of log ratio. |
Key Features
| Feature | Design Value |
|---|---|
| Trimmed 1V/decade gain | Factory-trimmed core ensures output changes exactly 1.000V per tenfold change in I₁/I₂ ratio-eliminates system-level gain calibration in absorbance meters. |
| Temperature-compensated VT | Internal matched transistors and tempco resistor (R1) cancel kT/q drift, enabling <±0.0005%/°C log conformity error over full 7.5-decade range. |
| Low input bias current | ±5pA (typ) at 25°C allows accurate measurement down to 100pA without significant error contribution-critical for low-light photodiode applications. |
| Configurable bandwidth | External CC capacitor (pin 3–8) lets designers trade off stability vs. speed: 45kHz BW at 1mA I₂ vs. 0.1kHz at 10nA I₂-enables adaptive response in multi-range instruments. |
| Single-supply operable | With external charge pump (e.g., TPS60402DBV), functions on +5V only-enables integration into battery-powered portable analyzers without dual-rail supplies. |
Applications
| Absorbance Measurement | 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: Computes log(D1/D2) to directly output absorbance A = log(λ₁′/λ₁), replacing software-based calculation. Use Value: Achieves 0.01% FSO accuracy over 5 decades, enabling detection of sub-0.001 AU absorbance changes in clinical analyzers. |
Use Scenario: Compressing wide-dynamic-range photocurrent (100pA–1mA) from silicon photodiodes in optical smoke detectors. IC Role / Device Role / Timing Role: Converts exponential photocurrent variation into linear voltage output for 12-bit ADC digitization. Use Value: Delivers effective 20-bit dynamic range from 12-bit ADC-reducing BOM cost while maintaining 100dB signal span. |
| Analog Front-End for A/D Converters | Avalanche Photodiode (APD) Monitoring |
Use Scenario: Preconditioning sensor outputs (e.g., gas sensors, pH electrodes) prior to 12-bit SAR ADC in handheld test equipment. IC Role / Device Role / Timing Role: Performs analog-domain log compression to maximize ADC utilization across 7.5 decades of input. Use Value: Eliminates need for programmable-gain amplifiers and range-switching logic-simplifying PCB layout and firmware. |
Use Scenario: Monitoring 3-decade APD current (100nA–100µA) in fiber-optic receiver modules operating at 10Gbps. IC Role / Device Role / Timing Role: Provides stable, temperature-invariant log ratio output for automatic gain control (AGC) feedback loops. Use Value: Maintains <±0.1mV/°C total error drift over –40°C to +85°C-ensuring consistent APD bias control in telecom hardware. |
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 (100MHz–4GHz), 65dB dynamic range, 2.7–5.5V single supply, no I₁/I₂ ratio capability. | Designed for RF power measurement-not suitable for DC/low-frequency photodiode or sensor current logging. | Select only for RF envelope detection; cannot replace LOG101AID in optical or precision DC log ratio systems. |
| LT1088CN8#PBF | Discrete-transistor log amp, 6-decade range (1nA–1mA), ±15V supply, 0.1% log conformity, no factory gain trim. | Requires manual gain/offset calibration; lacks integrated op-amps and temperature compensation of LOG101AID. | Use where cost sensitivity outweighs accuracy and temperature stability requirements; adds calibration overhead. |
Compared with ADL5513ACPZ-R7 and LT1088CN8#PBF, LOG101AID uniquely combines factory-trimmed 1V/decade gain, 7.5-decade DC current handling, and integrated temperature compensation-making it irreplaceable for high-accuracy, low-drift optical and analytical instrumentation.
Availability
LOG101AID 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 equipment programs.
Supply support for LOG101AID 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 decades of expertise in precision signal chain solutions.
LOG101AID belongs to TI's precision analog amplifier portfolio, designed specifically for high-accuracy logarithmic computation in optical, analytical, and industrial instrumentation where DC stability and wide dynamic range are critical.
FAQ
What is the maximum input current the LOG101AID can handle without performance degradation?
The LOG101AID maintains specified accuracy up to 3.5mA per input (I₁ or I₂), with absolute maximum rating of ±10mA. Exceeding 3.5mA increases nonlinearity; on ±5V supplies, total I₁ + I₂ must stay ≤4.5mA to avoid compliance issues. For higher currents, increase supply voltage beyond ±5V per datasheet guidance. LOG101AID's input protection does not include current limiting-external series resistors are recommended for transient overcurrent scenarios.
Can the LOG101AID operate from a single +5V supply?
Yes, the LOG101AID can operate from a single +5V supply when paired with a negative charge pump such as the TPS60402DBV, as shown in Figure 10 of the datasheet. This configuration generates the required negative rail internally, enabling use in portable or space-constrained designs. However, full 7.5-decade dynamic range requires adequate headroom-output swing is limited to (V–)+1.2V to (V+)-1.5V, so V– must be sufficiently negative to support the full log output span. LOG101AID's quiescent current remains ±1mA in this mode.
How does temperature affect LOG101AID's log conformity error?
LOG101AID's log conformity error increases with temperature: 0.0001%/°C over 5 decades (1nA–100µA) and 0.0005%/°C over 7.5 decades (100pA–3.5mA). At +85°C, total log conformity error reaches 0.06% FSO across the full range-still within specification. This drift is actively compensated by on-die temperature-sensitive resistors matching the kT/q coefficient of the bipolar core. LOG101AID's internal compensation eliminates need for external thermistors or digital correction in most industrial applications.
What is the purpose of the compensation capacitor (CC) between pins 3 and 8?
The compensation capacitor (CC) between pins 3 (GND) and 8 (I₂) stabilizes the LOG101AID's internal feedback loop and controls bandwidth. Its value determines frequency response: e.g., 150pF yields 38kHz BW at I₂ = 1µA, while 4500pF reduces BW to 0.1kHz at I₂ = 10nA. CC also affects step response asymmetry-rising/falling edges differ due to log amp nonlinearity. LOG101AID's datasheet provides minimum CC values per I₂/I₁ pair; undersizing causes oscillation, oversizing sacrifices speed. No CC is needed for pure DC applications.
Why are pins 2 and 5 labeled "NC" and what happens if they are connected?
Pins 2 and 5 of the LOG101AID are unconnected die pads with no internal bond wire-electrically and physically isolated. Connecting them to any net (ground, supply, or signal) introduces parasitic capacitance and potential leakage paths, degrading input bias current performance (<5pA typ) and increasing offset drift. The SOIC-8 package drawing confirms these pins have no internal connection. LOG101AID's functionality is fully defined by pins 1, 3, 4, 6, 7, and 8; pins 2 and 5 must remain floating per TI's layout recommendations.
LOG101AID 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:
- -
- 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
LOG101AID FAQ
1.How can I place an order for LOG101AID through Aetrix?
Please submit a Request for Quotation (RFQ) for LOG101AID 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 LOG101AID reliable?
The price and inventory of LOG101AID are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LOG101AID is usually 5 days.
3.What payment methods are accepted for LOG101AID?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LOG101AID transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LOG101AID?
LOG101AID orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LOG101AID 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 LOG101AID?
For technical support, including LOG101AID datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LOG101AID requirements.
6.How does Aetrix verify that LOG101AID is sourced from the original manufacturer or authorized distributors?
All LOG101AID 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 LOG101AID meets industry standards.
7.What is the process for return or replacement of LOG101AID?
All LOG101AID units undergo pre-shipment inspection (PSI). If there is an issue with LOG101AID, 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 LOG101AID part is unused and in its original packaging.
Return procedure for LOG101AID:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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