  We have integrated a commercial avalanche photodiode (APD) and the circuitry
needed to operate it as a single-photon detector (SPD) onto a single PC-board.
At temperatures accessible with Peltier coolers (~200-240K), the PCB-SPD
achieves high detection efficiency (DE) at 1308 and 1545 nm with low dark count
probability (e.g. ~10-6/bias pulse at DE=20%, 220 K), making it useful for
quantum key distribution (QKD). The board generates fast bias pulses, cancels
noise transients, amplifies the signals, and sends them to an on-board
discriminator. A digital blanking circuit suppresses afterpulsing.
