| 摘要 |
A gas sensor suitable for operation at a fixed temperature above ambient temperature comprises a gas sensitive MOSFET (10) which is maintained at the elevated temperature by virtue of the heat dissipated in the drain source path. A feedback circuit is provided for maintaining the power dissipation at a substantially fixed level, the source substrate diode (S-SB) of the device being used as a temperature sensor. In Figure 3 the source substrate diode is connected in a bridge circuit, an unbalance signal being detected by amplifier (14) and fed back via (FB) to the gate of the MOSFET (10) to influence the source-drain current LDS until the temperature is restored to the fixed value. The unbalance signal also provides the sensor output. In an alternative arrangement the output of amplifier (14) is applied to the gate of an FET source follower connected in the source drain current path of MOSFET (10) to alter the voltage drop across the latter to maintain the fixed temperature. <IMAGE> |
