| 摘要 |
PURPOSE:To improve S/N and to detect infrared rays precisely by providing two pyroelectric elements, two diodes, which are reversely connected to each other in parallel between output electrodes of the said elements, and two terminals by which outputs of the elements are provided through the respective FETs. CONSTITUTION:The diode 29, 30 are reversely connected to each other in parallel and are put between the electrodes 24, 34. In such a configuration, when voltages developed on the surface of the pyroelectric elements 22, 32 are very low, impedance becomes high. Accordingly outputs of the pyroelectric elements 22, 32 are individually impedance-converted or amplified by the FETs 25, 35 and appear at the output terminals 28, 38 as positive-negative symmetric reverse voltages. On the other hand, when the developed voltages are high, current flows through the diodes 29, 30 so that both developed voltages are neutralized due to a voltage-current relation corresponding to the developed voltage by the logarithmic characteristic of the diodes 29, 30, a very little current that overlaps the said current flows to make both the elements a connected state by dynamic impedance. Accordingly values that are attenuated a little are obtained, these are impedance-coverted or amplified by the FETs 25, 35. |
