LOG114 Status:ACTIVE

Product Information

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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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 V_LOGOUT 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.