LOG114 Texas instruments

LOG114

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LOG114

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Описание

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.

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

Scale factor (V/decade)	0.375
Input current range (min) (nA)	0.1
Input current range (max) (mA)	10
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
Conformity error (initial 5 decades) (max) (%)	0.2
Conformity error (initial 5 decades) (typ. over temp) (%/°C)	0.1
Operating temperature range (°C)	0 to 70
Specified voltage (±V)	5
Rating	Catalog