Abstract: In a photodetector amplifier scheme, the invention compensates for variations in photodetector quiescent current by sampling the amplifier output and subtracting a controllable current from the input to the amplifier. When a chopper or other modulator is used on the optical signal, the samples are taken periodically during the chopping cycle. This sampled signal is processed by a combination of gain and low pass filtering. The result of this processing controls a current source which subtracts a significant fraction of the average quiescent current from the total detector current. In a typical application, the amplifier is of the resettable current integrator type. In this case, the invention makes it possible to use smaller integration capacitors resulting in larger signals than if the quiescent current were not reduced by the operation of the invention. The gain, frequency response, and range of compensated quiescent currents and can be altered by changing timing signals.

Abstract: A temperature calibration substrate for producing increased temperature measurement accuracy. The temperature calibration substrate includes cavity means located below the surface of said substrate and thermocouple means disposed in the cavity for measuring the temperature of the substrate. The cavity means includes a cavity opening, an inner perimeter, and a length. Heat transfer means is disposed in the cavity means between the thermocouple means and the inner perimeter of the cavity means for transferring heat from the substrate to the thermocouple means. The cavity means is shaped to allow the thermocouple means to lay in close proximity to the substrate, and the thermocouple means is positioned substantially adjacent the inner perimeter of the cavity means and traverses the length of the cavity means thereby enhancing heat transfer efficiency from the substrate to the thermocouple means.