Abstract: In one embodiment, apparatus is provided with current optimization logic, a programmable current source for generating a reference current threshold, and current programming logic. In response to a plurality of input pulses received by a first TIA, the current optimization logic produces a series of digitized current values in response to i) a signal correlated to an output of the first TIA, to ii) a reference signal to which the output of the first TIA is compared. The current programming logic i) programs the programmable current source using ones of the series of digitized current values, until a predetermined condition is met, and then ii) locks the programmable current source to a most recent one of the digitized current values. In response to the reference current threshold, a second TIA produces the reference signal.