An analytical fit has been derived for the transfer function of a logarithmic electrometer utilizing a p‐n junction diode as a feedback loop element. Elementary semiconductor theory has been used to describe the diode current‐voltage characteristic, and the diode ohmic resistance and an external parallel resistance have been included in the circuit analysis. A temperature correction has been applied to account for a difference in the temperature of the diode during calibration and during the taking of data. The analytical fit with temperature correction is believed to be accurate to better than 10% of the absolute current input over seven current decades.