Biasing scheme for AC coupled strip detectors

A new biasing scheme for ac coupled strip detectors has been developed. Application of this scheme reduces the potential non-uniformity due to variations in the strip leakage currents. The circuit comprises an error amplifier that senses the strip current and compensates for the voltage drop across the biasing resistor. The error amplifier is powered by floating power supplies referenced to the bias voltage. A circuit was built that uses a low power amplifrer with femtoamp inputs. The circuit regulates the strip potential to within few mV of the bias voltage for strip currents between 0 and 5 nA with a 1.2G Omega biasing resistor. The circuit has been tested with a CZT strip detector.