Temperature compensated crystal oscillator

A temperature compensated crystal oscillator, comprising:

• oscillation means including a quartz crystal resonator and a control terminal, for providing an oscillating signal determined by the quartz crystal resonator and a control signal, the control signal being applied to the control terminal;
• temperature detecting means for detecting an operation temperature and outputting a temperature signal based on the operation temperature;
• and
• control signal generating means for receiving the temperature signal from the temperature detecting means, generating the control signal based on a characteristic curve, and outputting the control signal to the control terminal;
• the characteristic curve essentially consisting of a plurality of straight lines and being an approximation of an ideal control curve in a predetermined operation temperature range including the operation temperature, the ideal control curve having a relationship between the control signal and the temperature signal for ideally compensating a fluctuation of a frequency of the oscillating signal against changes of the operation temperature, the predetermined operation temperature range being divided into temperature ranges, each of the plurality of straight lines corresponding to one of the divided temperature ranges;
• wherein the control signal generating means includes a plurality of voltage function generating circuits each having input-output characteristics for linearly varying their respective output voltages in accordance with the temperature signal within a predetermined one of the divided temperature ranges and for maintaining their respective voltages at a first predetermined voltage in temperature ranges other than the one predetermined divided temperature range, and switching means for switching between the voltage function generating circuits, each of the voltage function generating circuits being operated in a corresponding one of the divided temperature ranges.

A temperature compensated crystal oscillator, comprising:

• oscillation means including a quartz crystal resonator and a control terminal, for providing an oscillating signal determined by the quartz crystal resonator and a control signal, the control signal being applied to the control terminal.;
• temperature detecting means for detecting an operation temperature and outputting a temperature signal based on the operation temperature;
• and
• control signal generating means for receiving the temperature signal from the temperature detecting means, generating the control signal based on a characteristic curve, and outputting the control signal to the control terminal;
• the characteristic curve essentially consisting of a plurality of straight lines and being an approximation of an ideal control curve in a predetermined operation temperature range including the operation temperature, the ideal control curve having a relationship between the control signal and the temperature signal for ideally compensating a fluctuation of a frequency of the oscillating signal against changes of the operation temperature, the predetermined operation temperature range being divided into temperature ranges, each of the plurality of straight lines corresponding to one of divided temperature ranges,
• wherein the control signal generating means includes:
• a number (n+1) of voltage function generating circuits having input-output characteristics such that, in a predetermined input voltage range corresponding to two adjoining ones of the divided temperature ranges, an output voltage linearly increases from zero to a predetermined maximum value in accordance with input voltage in a first one or the two adjoining temperature ranges and that the output voltage linearly decreases from the maximum value to zero in accordance with the input voltage in the other one of the two adjoining temperature ranges and further that the output voltage is zero in an input voltage range other than the input voltage range corresponding to the two adjoining temperature ranges;
• and a voltage adder for adding the output voltages of all the voltage function generating circuits with one another,
• wherein the output voltage of each voltage function generating circuit varies based on the following relationship:
• as the output voltage of an i.sub.th voltage function generating circuit increases from zero to a maximum value, the output voltage of an (i-1).sub.th voltage function generating circuit decreases from a maximum value to zero;
• and
• as the output voltage of an i.sub.th voltage function generating circuit decreases from a maximum value to zero, the output voltage of an (i+1).sub.th voltage function generating circuit increases from zero to a maximum value,
• wherein n is an integer of 2 or more representing the number of temperature ranges;
• and i is an integer in the range of 2 to n.