The LOG102AID is a versatile Amplifier IC that computes the logarithm or log ratio of an input current relative to a reference current. The LOG102 is tested over a wide dynamic range of input signals. In log ratio applications, a signal current can be generated by a photodiode and a reference current from a resistor in series with a precision external voltage reference. In the block diagram shown below, A3 and A4 are identical, uncommitted op-amps that can be used for a variety of functions, such as filtering, offsetting, adding gain or as a comparator to detect loss of signal. The output signal at VLOG OUT is trimmed to 1V per decade of input current. It can be scaled with an output amplifier, either A3 or A4. Low DC offset voltage and temperature drift allow accurate measurement of low-level signals over a wide environmental temperature range.
Easy-to-use complete log ratio function
Output amplifiers for scaling and signal loss indication
High accuracy - 0.15% FSO total error over 6 decades
