The AD8305ACPZ-RL7 is an inexpensive microminiature Logarithmic Converter optimized for determining optical power in fibre optic systems. It uses an advanced implementation of a classic translinear (junction based) technique to provide a large dynamic range in a versatile and easily used form. A single-supply voltage of between 3 and 12V is adequate, dual supplies may optionally be used. The low quiescent current (typically 5mA) permits use in battery-operated applications. The input current, IPD, of 10nA to 1mA applied to the INPT pin is the collector current of an optimally scaled NPN transistor, which converts this current to a voltage (VBE) with a precise logarithmic relationship. A second such converter is used to handle the reference current (IREF) applied to pin IREF. These input nodes are biased slightly above ground (0.5V). This is generally acceptable for photodiode applications where the anode does not need to be grounded.
Optimized for fibre optic photodiode interfacing
Measures current over 5 decades
Full log-ratio capabilities
Nominal slope of 10mV/dB (200mV/decade)
Nominal intercept of 1nA (set by external resistor)
(EN)
