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Texas Instruments 4127JG
- Part No.:
- 4127JG
- Manufacturer:
- Texas Instruments
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 24-CDIP (0.600", 15.24mm)
- Datasheet:
-
4127JG.pdf
- Description:
- IC LOGARITHMIC 2 CIRCUIT 24CDIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,381
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Product details
Overview
4127JG from Texas Instruments (formerly Burr-Brown) is a hybrid logarithmic amplifier IC that accepts bipolar input currents (±1nA to ±1mA) and voltages (±1mV to ±10V), delivers ±10V log output with 1% initial log conformity, and integrates a current inverter and uncommitted op amp for log ratio, antilog, and signal conditioning in precision analog front-ends.
For engineers reviewing the 4127JG datasheet, 4127JG pinout, 4127JG application, or 4127JG equivalent, this device supports high-dynamic-range compression in photodiode interfaces, transducer linearization in analytical instruments, and dual-signal log-ratio computation in medical sensor systems - all requiring verified bipolar input handling and drift-stable scaling.
Technical Context
The 4127JG implements a monolithic quad-transistor logarithmic core with temperature-compensated gain elements (520Ω thermistor RT) and FET-input op amps (A1, A3) to achieve stable log conversion across six decades of current. Its internal current inverter enables true bipolar current logging without external polarity-reversal circuitry.
Pin-programmable operation includes logarithmic (EO = –A log|IS|/IR), log-ratio (EO = –A log|I1|/|I2|), and antilog modes (via external RO–IR feedback). Scale factor "A" (1–10V) and reference current IR (100nA–1mA) are set by external resistors R2 and R1, respectively, with trimmable accuracy.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Log Conformity Accuracy | 1% max over ±1nA to ±1mA input range at +25°C - defines maximum deviation from ideal log transfer function in production units. |
| Input Dynamic Range | 6 decades current (1nA–1mA), 4 decades voltage (1mV–10V) - enables single-device compression of ultra-low to medium-level sensor signals. |
| Output Voltage Range | ±10V into 10Ω load - provides full-rail analog output compatible with 12-bit ADCs and industrial PLC inputs. |
| Small-Signal Bandwidth | 90kHz at 100µA input - supports real-time logging of fast-varying photodiode or current-loop signals. |
| Supply Requirements | ±15VDC (±14V to ±16V), quiescent current ≤ ±20mA - mandates dual-rail lab or instrumentation power supplies. |
| Temperature Range | Operating: –10°C to +70°C; Specified: 0°C to +60°C - limits use to non-automotive, controlled-environment applications. |
| Reference Current Drift | ±0.001 IR/°C for IR ≥ 1µA - ensures stable scaling over ambient variations when using ≥1µA reference. |
Pinout & Package
Packaged in a 24-pin ceramic dual-in-line package (CDIP) with 0.600" wide body and hermetic seal, the 4127JG uses a hybrid construction combining monolithic log-core die and discrete passive compensation elements for long-term stability.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | +I Input | Positive current input node; accepts +1nA to +1mA; internally tied to Pin 5. |
| 2 | IREF Input | Reference current programming input; accepts +1µA to +1mA for setting IR. |
| 4 | +I Input (Tied) | Internally connected to Pin 1; redundant positive current entry point. |
| 5 | +I Input (Tied) | Internally connected to Pin 1; used for layout symmetry and noise rejection. |
| 7 | –I Input | Negative current input node; accepts –1nA to –1mA via integrated current inverter. |
| 10 | Log Output | Main logarithmic output voltage EO = –A log|IS|/IR; ±10V swing, 10Ω source impedance. |
| 11 | Gain Adjust | Connects to external R2 to set scale factor "A"; adjusts output volts per decade. |
| 14 | Op Amp –Input | Inverting input of uncommitted op amp; usable as buffer, filter, or gain stage. |
| 18 | Op Amp +Input | Non-inverting input of uncommitted op amp; high-impedance FET node (1MΩ). |
| 19 | Op Amp Output | Output of uncommitted op amp; ±5mA drive capability, 85dB large-signal gain. |
| 21 | Common | Analog ground reference; must be low-impedance connection to system AGND. |
| 22 | Negative Supply | –15VDC supply pin; decoupling capacitor required near pin. |
| 23 | Positive Supply | +15VDC supply pin; decoupling capacitor required near pin. |
Key Features
| Feature | Design Value |
|---|---|
| Bipolar input acceptance | Processes both positive and negative current/voltage inputs without external polarity switching - eliminates relay or analog switch complexity in bidirectional sensor interfaces. |
| Integrated current inverter | Converts negative input current to equivalent positive current internally - enables true log-of-absolute-value operation with no added components. |
| Pin-programmable log/antilog/log-ratio | Configured via external resistor networks on Pins 2, 11, and 19 - supports three distinct transfer functions in one package without redesign. |
| Uncommitted FET-input op amp | Provides 40nA bias current, 5mV offset, and 85dB gain - usable as post-log buffer, active filter, or gain stage without adding an external amplifier. |
| Drift-optimized monolithic core | Uses matched transistor quad and temperature-compensating thermistor (RT ≈ 520Ω) - achieves <0.0005A/°C scale factor drift for stable multi-decade logging. |
Applications
| Photodiode Signal Compression | Transducer Linearization |
|---|---|
|
Use Scenario: Wide-dynamic-range optical detection in spectrophotometers where photocurrent varies from 10nA (low absorbance) to 100µA (high absorbance). IC Role / Device Role / Timing Role: Logarithmic amplifier converting photocurrent to linearized voltage output proportional to optical density. Use Value: Replaces 60dB+ programmable-gain amplifier stages with single-chip solution, reducing component count and thermal drift errors. |
Use Scenario: Linearizing output of platinum RTD or thermocouple sensors whose resistance/EMF vs. temperature follows exponential curves. IC Role / Device Role / Timing Role: Precision log converter transforming nonlinear sensor output into linear voltage for direct ADC digitization. Use Value: Achieves <1% nonlinearity over 4-decade input range without microcontroller-based lookup tables or calibration firmware. |
| Medical pH/ISE Sensor Interface | Process Control Log Ratio Monitoring |
|
Use Scenario: Ion-selective electrode (ISE) measurements in blood analyzers where millivolt-level Nernst potentials require high-impedance, low-drift amplification. IC Role / Device Role / Timing Role: High-Z FET-input logarithmic front-end converting mV-level electrode potential to compressed voltage scale. Use Value: Enables accurate pH measurement across 0–14 range using ±10V full-scale output, avoiding saturation at extreme pH values. |
Use Scenario: Real-time monitoring of gas concentration ratios (e.g., O₂/N₂) in combustion control systems using dual thermal conductivity sensors. IC Role / Device Role / Timing Role: Log-ratio amplifier computing EO = –A log|I₁|/|I₂| to directly output concentration ratio independent of absolute sensor gain drift. Use Value: Delivers drift-immune ratio measurement without recalibration, leveraging matched internal current sources and quad-transistor matching. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar logarithmic amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD8304ACPZ-R7 | Monolithic 80dB log amp (10pA–1mA), 2.7–5.5V single supply, no bipolar input support. | Limited to unidirectional current sensing; lacks current inverter and uncommitted op amp. | Choose for battery-powered, low-voltage, single-polarity applications where size and supply simplicity outweigh bipolar capability. |
| LM3915N-1 | LED driver IC with built-in log decoder; 30dB range, no analog output, no programmable scaling. | Designed for visual display only; cannot interface to ADCs or downstream analog processing. | Choose only for basic bar-graph indication; not a functional substitute for analog log conversion or signal processing. |
Compared with AD8304ACPZ-R7 and LM3915N-1, the 4127JG uniquely supports bipolar current logging, integrated log-ratio computation, and a configurable op amp - making it irreplaceable in precision instrumentation requiring multi-function analog signal conditioning within a single hybrid package.
Availability
4127JG is available at Aetrix Electronics and suitable for photodiode compression, transducer linearization, and medical sensor interfacing requiring stable component supply under extended lifecycle management.
Supply support for 4127JG 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 (TI) acquired Burr-Brown in 2000 and maintains legacy analog product support, including precision amplifiers, data converters, and signal-conditioning ICs.
The 4127JG belongs to TI's heritage high-accuracy analog signal-processing portfolio, designed specifically for laboratory instrumentation, analytical equipment, and medical diagnostics where multi-decade dynamic range and bipolar signal integrity are critical.
FAQ
What is the guaranteed log conformity accuracy of the 4127JG over its full input range?
The 4127JG guarantees ≤1% log conformity accuracy over its specified current input range of ±1nA to ±1mA and voltage input range of ±1mV to ±10V at +25°C. This specification reflects maximum deviation from the ideal logarithmic transfer function EO = –A log|IS|/IR and is validated per the 4127JG datasheet test conditions using calibrated current and voltage sources.
Can the 4127JG accept negative input voltages, and how is this achieved?
Yes, the 4127JG accepts negative input voltages (down to –10V) using its internal current inverter and precision op-amp architecture. Negative voltage inputs are converted to proportional negative currents at Pin 7, then inverted to positive current for logarithmic processing - enabling true bipolar voltage logging without external level-shifting circuitry. This behavior is confirmed in the 4127JG functional diagram and Figure 5 of its datasheet.
Does the 4127JG include an operational amplifier, and what are its key electrical characteristics?
Yes, the 4127JG integrates an uncommitted FET-input operational amplifier (Pins 14, 18, 19) with 5mV input offset voltage, 40nA input bias current, 1MΩ input impedance, 85dB large-signal voltage gain, and ±5mA output drive capability. This op amp is fully accessible for buffering, filtering, or gain staging - a feature absent in most monolithic log amps and explicitly documented in the 4127JG "Uncommitted Op Amp Characteristics" table.
What is the recommended supply configuration for stable operation of the 4127JG?
The 4127JG requires tightly regulated ±15VDC supplies (operable from ±14V to ±16V), with separate decoupling capacitors (≥10µF tantalum + 0.1µF ceramic) placed within 5mm of Pins 22 (–15V) and 23 (+15V). Ground connections must route to a low-impedance analog common (Pin 21) to minimize noise coupling - a requirement emphasized in the 4127JG layout guidelines and verified in its stability test conditions.
Is the 4127JG suitable for log-ratio applications, and how is this configured?
Yes, the 4127JG supports log-ratio operation (EO = –A log|I₁|/|I₂|) using its dual current inputs (Pins 1/4/5 for I₁, Pin 7 for I₂) and internal reference current generator. Configuration requires external resistors R1 (for IR) and R2 (for A), with I₂ ≥ 1µA and |I₁| ≥ 1nA - a capability explicitly detailed in Figures 6–8 and the "Log Ratio Operation" section of the 4127JG datasheet.
4127JG Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 24-CDIP (0.600", 15.24mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Amplifier Type:
- Logarithmic
- Number of Circuits:
- 2
- Output Type:
- -
- Slew Rate:
- -
- Gain Bandwidth Product:
- -
- -3db Bandwidth:
- 90 kHz
- Current - Input Bias:
- 40 nA
- Voltage - Input Offset:
- 5 mV
- Current - Supply:
- 20mA
- Current - Output / Channel:
- 5 mA
- Voltage - Supply Span (Min):
- 28 V
- Voltage - Supply Span (Max):
- 32 V
- Operating Temperature:
- -10°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 24-CDIP
4127JG FAQ
1.How can I place an order for 4127JG through Aetrix?
Please submit a Request for Quotation (RFQ) for 4127JG 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 4127JG reliable?
The price and inventory of 4127JG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 4127JG is usually 5 days.
3.What payment methods are accepted for 4127JG?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 4127JG transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 4127JG?
4127JG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 4127JG 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 4127JG?
For technical support, including 4127JG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 4127JG requirements.
6.How does Aetrix verify that 4127JG is sourced from the original manufacturer or authorized distributors?
All 4127JG 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 4127JG meets industry standards.
7.What is the process for return or replacement of 4127JG?
All 4127JG units undergo pre-shipment inspection (PSI). If there is an issue with 4127JG, 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 4127JG part is unused and in its original packaging.
Return procedure for 4127JG:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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