LOG114 Precision High-Speed Logarithmic Amplifier with 2.5V Reference and Uncommitted Output Op Amps | TI.com

LOG114 (ACTIVE)

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

 

Description

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.

Features

  • 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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Parametrics

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Part number Order Scale factor (V/decade) Input current range (Min) (nA) Input current range (Max) (mA) Conformity error (initial 5 decades) (Max) (%) Conformity error (initial 5 decades) (typ. over temp) (%/degree C) Offset voltage (input amplifiers) (Max) (mV) Vs (+/-) (Min) (V) Vs (+/-) (Max) (V) Iq (Max) (mA) Reference type Auxiliary op amps Full-scale output voltage (Min) (+/- V) Full-scale output voltage (Max) (+/- V) Operating temperature range (C) Package Group Package size: mm2:W x L (PKG) Specified voltage (+/- V)
LOG114 Order now 0.375     0.1     10     0.2     0.1     4     4.8     11     15     Internal     2     -4.4     4.4     0 to 70     VQFN | 16     16VQFN: 16 mm2: 4 x 4 (VQFN | 16)     5