  The Pound-Drever-Hall laser stabilization technique requires a fast,
low-noise photodetector. We present a simple photodetector design that uses a
transformer as an intermediary between a photodiode and cascaded low-noise
radio-frequency amplifiers. Our implementation using a silicon photodiode
yields a detector with 50 MHz bandwidth, gain $> 10^5$ V/A, and input current
noise $< 4$ pA/$\sqrt{\mathrm{Hz}}$, allowing us to obtain shot-noise-limited
performance with low optical power.
