Among the classes of logarithmic amplifiers, the DC log amp continues to be a very powerful, cost-effective solution for compressing wide-dynamic-range sensor signals. This article derives the overall DC log amp transfer function from the VBE-to-IC transfer characteristic of bipolar transistors. It discusses the circuit blocks encountered in a modern-day integrated DC log amp, the various errors affecting log amp performance, and a design example featuring the MAX4206. Finally, suggestions for optimizing log amp performance through calibration and design pointers are detailed.