Oscillator
Across the entire operating temperature range, and without requiring a new transistor element, the constant voltage output by a constant voltage circuit can be controlled to a voltage greater than or equal to the stop-oscillating voltage and as low as possible. A resistance 11 b that negatively feeds back a reference current Iref is connected between the gate and source of a depletion mode n-channel transistor 11 a configured to produce the reference current Iref on which the constant voltage VREG is based. The resistance of resistance 11 b has a gradient to temperature change of the same sign as the gradient of the difference between the constant voltage and the stop-oscillating voltage to temperature change when the gradient of the resistance value of the resistance to temperature change is 0.
1. An oscillator comprising:
a constant voltage circuit including a constant current source that generates a reference current, and a constant voltage generator that generates a constant voltage according to the reference current; and
an oscillation circuit configured to oscillate when the constant voltage is applied, and stop oscillating when the constant voltage goes to or below a stop-oscillating voltage in a specific temperature range;
the constant current source including:
a depletion mode transistor configured to produce the reference current; and
a feedback element connected between a gate and source of the transistor;
a resistance of the feedback element having a gradient to temperature change whereby the gradient of a difference between the constant voltage and the stop-oscillating voltage to temperature change is 0.
2. The oscillator described in claim 1 , wherein:
the constant voltage increases as the reference current increases; and
when the gradient of the resistance of the feedback element to temperature change is 0, a sign of the gradient of the resistance of the feedback element to temperature change is the same as a sign of the gradient of the difference between the constant voltage and the stop-oscillating voltage to temperature change.
3. The oscillator described in claim 1 , wherein:
the constant voltage generator produces a constant voltage that decreases as the reference current increases; and
when the gradient of the resistance of the feedback element to temperature change is 0, a sign of the gradient of the resistance of the feedback element to temperature change is the different from a sign of the gradient of the difference between the constant voltage and the stop-oscillating voltage to temperature change.
4. The oscillator described in claim 1 , wherein the feedback element is a resistance.
5. A timepiece movement comprising an oscillator as described in claim 1 .
6. A timepiece comprising a timepiece movement as described in claim 5 .