apd the pin photodiode does not mandate high voltages but values on the order of 10 v are relatively common u2014 to help reduce diode capacitance for bandwidth optimization the pin is more easily integrated with other technologies and available in array format apds and pins have similar quantum efficiencies for given semiconductor material hence a real issue to face in designing a suitable pin based detector 12 is that of obtaining gains equivalent to the apd but equal to or better noise performance equivalent noise performance is still significant when integration and scaling are considered the accepted and now best way to obtain gain with a pin is to use the same gain stage that would be used for an apd such a stage includes an op amp 16 configured for transimpedance gain or a transimpedance amplifier tia 116 in preferred embodiments a tia 116 fig2 is used to feed a digitally swept time resolving subsystem the tia is implemented using an op amp 16 the noninverting case can be substituted with a slight loss of bandwidth the tia 116 is an op amp 16 configured to amplify a current signal while using it to develop a corresponding voltage hence the name the tia 116 can be customized to meet specific needs or uses of the system principal areas of customization for the tia 116 are a minimizing the impact of the photodiode capacitance through selection of applied bias voltage or through isolation of the corresponding op amp 16 input using an active element such as a common base field effect transistor fet b optimizing gain and overall bandwidth through the selection of op amp 16 feedback.