The LOG114AIRGVT is a precision high-speed Logarithmic Amplifier designed for measuring low-level and wide dynamic range currents in communications and lasers. 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 5 or 10V range.
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