Patent ID: 8223036

Claim:
In a telemetry system for use in an internal combustion engine, a circuit structure affixed to a moving part of said engine for amplifying information sensed about a condition of said moving part, said circuit structure being adapted for the high temperature environment of said engine and comprising: a differential amplifier having an input for receiving a signal from a sensor disposed on said part, the signal being representative of the condition of said part; and, said differential amplifier comprising a transistor having a gate bias network with a first resistive element having a positive temperature coefficient of resistance coupled between a source of positive voltage and the gate terminal of said transistor and a second resistive element having a zero temperature coefficient of resistance coupled between said gate terminal of said transistor and ground potential, whereby as the temperature increases the bias voltage at the gate terminal of said transistor decreases; further comprising a third resistive element having a positive temperature coefficient of resistance coupled between the drain terminal of said transistor and said source of positive potential, whereby as the temperature increases the gain of said amplifier remains the same.