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LOG114

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Precision High-Speed Logarithmic Amplifier with 2.5V Reference and Uncommitted Output Op Amps

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Data sheet
Precision High-Speed Logarithmic Amplifier with 2.5V Reference and Uncommitted Output Op Amps

LOG114

ACTIVE
Data sheet Order now

Product details

Scale factor (V/decade) 0.375 Input current range (Min) (nA) 0.1 Input current range (Max) (mA) 10 Conformity error (initial 5 decades) (Max) (%) 0.2 Conformity error (initial 5 decades) (typ. over temp) (%/degree C) 0.1 Offset voltage (input amplifiers) (Max) (mV) 4 Vs (+/-) (Min) (V) 4.8 Vs (+/-) (Max) (V) 11 Iq (Max) (mA) 15 Dynamic range (Typ) (dB) 160 Reference type Internal Auxiliary op amps 2 Full-scale output voltage (Min) (+/- V) -4.4 Full-scale output voltage (Max) (+/- V) 4.4 Operating temperature range (C) 0 to 70 Specified voltage (+/- V) 5
Scale factor (V/decade) 0.375 Input current range (Min) (nA) 0.1 Input current range (Max) (mA) 10 Conformity error (initial 5 decades) (Max) (%) 0.2 Conformity error (initial 5 decades) (typ. over temp) (%/degree C) 0.1 Offset voltage (input amplifiers) (Max) (mV) 4 Vs (+/-) (Min) (V) 4.8 Vs (+/-) (Max) (V) 11 Iq (Max) (mA) 15 Dynamic range (Typ) (dB) 160 Reference type Internal Auxiliary op amps 2 Full-scale output voltage (Min) (+/- V) -4.4 Full-scale output voltage (Max) (+/- V) 4.4 Operating temperature range (C) 0 to 70 Specified voltage (+/- V) 5
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VQFN (RGV) 16 16 mm² 4.0 x 4.0
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  • ADVANTAGES:
    • - Tiny for High Density Systems
    • - Precision on One Supply
    • - Fast Over Eight Decades
    • - Fully-Tested Function
  • TWO SCALING AMPLIFIERS
  • WIDE INPUT DYNAMIC RANGE: Eight Decades, 100pA to 10mA
  • 2.5V REFERENCE
  • STABILE OVER TEMPERATURE
  • LOW QUIESCENT CURRENT: 10mA
  • DUAL OR SINGLE SUPPLY: ±5V, +5V
  • PACKAGE: Small QFN-16 (4mm x 4mm)
  • SPECIFIED TEMPERATURE RANGE: –5°C to +75°C
  • APPLICATIONS
    • ONET ERBIUM-DOPED FIBER OPTIC AMPLIFIER (EDFA)
    • LASER OPTICAL DENSITY MEASUREMENT
    • PHOTODIODE SIGNAL COMPRESSION AMP
    • LOG, LOG-RATIO FUNCTION
    • ANALOG SIGNAL COMPRESSION IN FRONT OF ANALOG-TO-DIGITAL (ADC) CONVERTER
    • ABSORBANCE MEASUREMENT
  • ADVANTAGES:
    • - Tiny for High Density Systems
    • - Precision on One Supply
    • - Fast Over Eight Decades
    • - Fully-Tested Function
  • TWO SCALING AMPLIFIERS
  • WIDE INPUT DYNAMIC RANGE: Eight Decades, 100pA to 10mA
  • 2.5V REFERENCE
  • STABILE OVER TEMPERATURE
  • LOW QUIESCENT CURRENT: 10mA
  • DUAL OR SINGLE SUPPLY: ±5V, +5V
  • PACKAGE: Small QFN-16 (4mm x 4mm)
  • SPECIFIED TEMPERATURE RANGE: –5°C to +75°C
  • APPLICATIONS
    • ONET ERBIUM-DOPED FIBER OPTIC AMPLIFIER (EDFA)
    • LASER OPTICAL DENSITY MEASUREMENT
    • PHOTODIODE SIGNAL COMPRESSION AMP
    • LOG, LOG-RATIO FUNCTION
    • ANALOG SIGNAL COMPRESSION IN FRONT OF ANALOG-TO-DIGITAL (ADC) CONVERTER
    • ABSORBANCE MEASUREMENT
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The LOG114 is specifically designed for measuring low-level and wide dynamic range currents in communications, lasers, medical, and industrial systems. The device computes the logarithm or log-ratio of an input current or voltage relative to a reference current or voltage (logarithmic transimpedance amplifier).

High precision is ensured over a wide dynamic range of input signals on either bipolar (±5V) or single (+5V) supply. Special temperature drift compensation circuitry is included on-chip. In log-ratio applications, the signal current may be from a high impedance source such as a photodiode or resistor in series with a low impedance voltage source. The reference current is provided by a resistor in series with a precision internal voltage reference, photo diode, or active current source.

The output signal at VLOGOUT has a scale factor of 0.375V out per decade of input current, which limits the output so that it fits within a 5V or 10V range. The output can be scaled and offset with one of the available additional amplifiers, so it matches a wide variety of ADC input ranges. Stable dc performance allows accurate measurement of low-level signals over a wide temperature range. The LOG114 is specified over a -5°C to +75°C temperature range and can operate from -40°C to +85°C.

The LOG114 is specifically designed for measuring low-level and wide dynamic range currents in communications, lasers, medical, and industrial systems. The device computes the logarithm or log-ratio of an input current or voltage relative to a reference current or voltage (logarithmic transimpedance amplifier).

High precision is ensured over a wide dynamic range of input signals on either bipolar (±5V) or single (+5V) supply. Special temperature drift compensation circuitry is included on-chip. In log-ratio applications, the signal current may be from a high impedance source such as a photodiode or resistor in series with a low impedance voltage source. The reference current is provided by a resistor in series with a precision internal voltage reference, photo diode, or active current source.

The output signal at VLOGOUT has a scale factor of 0.375V out per decade of input current, which limits the output so that it fits within a 5V or 10V range. The output can be scaled and offset with one of the available additional amplifiers, so it matches a wide variety of ADC input ranges. Stable dc performance allows accurate measurement of low-level signals over a wide temperature range. The LOG114 is specified over a -5°C to +75°C temperature range and can operate from -40°C to +85°C.

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Technical documentation

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Type Title Date
* Data sheet Single-Supply, High-Speed, Precision Logarithmic Amplifier datasheet (Rev. A) 19 Mar 2007
User guide LOG114EVM User Guide 29 Sep 2011

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Evaluation board

LOG114EVM — LOG114 Evaluation Module

The LOG114EVM is a ready-to-use platform for evaluating the performance of the LOG114 in various configurations.The LOG114EVM comes configured to operate on a single 5-V power supply. The circuit used in the LOG114EVM is designed to operate over a wide range of input currents (10 nA to 10 mA) and (...)

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Simulation model

LOG114 PSpice Model (Rev. C)

SBOM383C.ZIP (53 KB) - PSpice Model
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Simulation model

LOG114 TINA-TI Reference Design (Rev. C)

SBOM384C.TSC (101 KB) - TINA-TI Reference Design
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Simulation model

LOG114 TINA-TI Spice Model (Rev. C)

SBOM385C.ZIP (5 KB) - TINA-TI Spice Model
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Simulation tool

PSPICE-FOR-TI — PSpice® for TI design and simulation tool

PSpice® for TI is a design and simulation environment that helps evaluate functionality of analog circuits. This full-featured, design and simulation suite uses an analog analysis engine from Cadence®. Available at no cost, PSpice for TI includes one of the largest model libraries in the (...)
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Simulation tool

TINA-TI — SPICE-based analog simulation program

TINA-TI provides all the conventional DC, transient and frequency domain analysis of SPICE and much more. TINA has extensive post-processing capability that allows you to format results the way you want them. Virtual instruments allow you to select input waveforms and probe circuit nodes voltages (...)
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