Diffusion and photoetching technology enable one to diffuse a well defined layer having a high temperature coefficient of resistance on the surface of a silicon chip. The resistance and the temperature coefficient can be tailored to optimize the device for use as a bolometer at any operating temperature between 1K and 4.2K and possibly much lower. A new type of device is described in which a thin film heater has been evaporated onto the insulating surface of the bolometer. This enables one to directly calibrate the bolometer's response to absorbed power. The heater is useful in situations where the background power changes from one measurement to the next and one wishes to calibrate the bolometer in situ. The performance characteristics as a function of background power can easily be measured with the heater. A description of the device and performance data are presented.