A High Sensitivity Semiconductor Diode Modulator for DC Current Measurement

A semiconductor diode modulator will be described capable of measuring dc currents down to 10-10 to 10-11 amperes. This modulator utilizes one diode although a second is normally installed for balance purposes in high sensitivity measurements. The modulator utilizes pulse techniques instead of sine waves which makes possible the high sensitivity. The circuit details of the modulator and design criteria will be discussed.