Crystal oscillator temperature compensating circuit
 An integratable circuit is utilized for generating a temperature varying control voltage to be applied to a varactor diode to temperature compensate a crystal oscillator. The temperature compensating circuit has a middle range circuit for creating a substantially linear current versus temperature variation in a middle temperature range, a cold-temperature range circuit operative below a predetermined temperature for creating a non-linear current versus temperature variation a hot-temperature range circuit operative above a predetermined temperature for creating a non-linear current versus temperature variation and circuitry for summing said currents and generating a voltage proportional to the current sum. The control circuit, which requires a regulated supply voltage, uses a diode string and differential amplifiers to generate the desired current versus temperature variation. 
Motorola, Inc.
H
H03L
inventional
Anthony F. Albert V.
Keller Kraybill