We've published our first full-scale application note: AN-1: Photoreceiver Testing System. Based on our LP870 Nanosecond Light Source and LA22 Lab Amplifier, the system gives an easy and economical way to test photoreceivers as fast as 5 ns. In the time domain, it measures rise and fall times with excellent accuracy. In the frequency domain, it measures the noise floor (down to below 1 nV/√Hz), both dark and light, and gives a neat hack for measuring the transimpedance vs. frequency to very high accuracy.