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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|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)|
||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|