Oscillators – With device responsive to external physical condition – Temperature or light responsive
Patent
1985-04-25
1986-07-29
LaRoche, Eugene R.
Oscillators
With device responsive to external physical condition
Temperature or light responsive
331108D, 331116R, 374183, G01K 700
Patent
active
046033068
ABSTRACT:
An oscillator circuit for sensing and indicating temperature by changing oscillator frequency with temperature comprises a programmable operational amplifier which is operated on the roll-off portion of its gain versus frequency curve and has its output directly connected to the inverting input to place the amplifier in a follower configuration. Its output is also connected to the non-inverting input by a capacitor with a crystal or other tuned circuit also being connected to the non-inverting input. A resistor is connected to the program input of the amplifier to produce a given set current at a given temperature, the set current varying with temperature. As the set current changes, the gain-bandwidth of the amplifier changes and, in turn, the reflected capacitance across the crystal changes, thereby providing the desired change in oscillator frequency by pulling the crystal. There is no requirement that a crystal employed with this circuit display either a linear frequency change with temperature or a substantial frequency change with temperature.
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LaRoche Eugene R.
Lee James C.
Manning John R.
Sandler Ronald F.
The United States of America as represented by the Administrator
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