Oscillating apparatus with adjustable oscillating frequency

1. An oscillating apparatus, comprising:

a biasing circuit, for dynamically adjusting a bias signal of the oscillating apparatus, comprising:

a connecting port, for coupling an impedance device to control a frequency of an oscillating signal or for coupling a clock source to receive a reference clock;

a detecting circuit, coupled to the connecting port, for detecting whether the connecting port is coupled to the impedance device or the clock source for generating a selection signal;

a selecting circuit, comprising an AND gate coupled to a multi-vibrator and the selection signal, and an OR gate coupled to the AND gate and the connecting port; and

the multi-vibrator, coupled to the biasing circuit, for generating the oscillating signal according to the biasing signal.

2. The apparatus of claim 1 , wherein the biasing circuit comprises:

a first impedance device;

a first cascoded transistor, comprising a first transistor cascoded on a second transistor, a first terminal of the first transistor coupled to a first voltage level, a second terminal of the first transistor coupled to a first terminal of the second transistor, a second terminal of the second transistor coupled to a control terminal of the first transistor, control terminals of the first and second transistors coupled to two ends of the first impedance device, respectively;

a second cascoded transistor, comprising a third transistor cascoded on a fourth transistor, a first terminal of the third transistor coupled to the first voltage level, a second terminal of the third transistor coupled to the first terminal of the fourth transistor; and

a current mirror, comprising: a first current path, couple to second terminal of the fourth transistor and a second voltage level; and

a second current path, couple to the control terminal of the second transistor and the second voltage level.

3. The apparatus of claim 2 further comprising:

a second impedance device, having two ends coupled to the second current

path and the second voltage level respectively, for controlling a frequency of the oscillating signal.

4. The apparatus of claim 3 , wherein the biasing circuit and the multi-vibrator are positioned in a chip, and the second impedance device is positioned off the chip.

5. The apparatus of claim 2 , wherein the biasing circuit further comprises:

a capacitor device, having two ends coupled to the first current path and the second terminal of the first transistor, for avoiding the biasing circuit from oscillating.

6. The apparatus of claim 1 , wherein the detecting circuit generates the selection signal according to a voltage level at the connecting port.

7. The apparatus of claim 6 , wherein the detecting circuit comprises:

a capacitor device; and

a transistor, having a control terminal coupled to the connecting, a first terminal coupled to a first voltage level of the capacitor for outputting the selection signal, and a second terminal coupled to a second voltage level.

8. An oscillating apparatus, comprising:

a biasing circuit, for generating at least a biasing signal, wherein the biasing circuit comprises a connecting port, for coupling an impedance device to control a frequency of an oscillating signal or for coupling a clock source to receive a reference clock;

a detecting circuit, coupled to the connecting port, for detecting whether the connecting port is coupled to the impedance device or the clock source for generating a selection signal;

a selecting circuit, comprising an AND gate coupled to an oscillator and the selection signal, and an OR gate coupled to the AND gate and the connecting port; and

the oscillator, coupled to the biasing circuit, for generating the oscillating signal according to the biasing signal.

9. The apparatus of claim 8 , wherein the detecting circuit generates the selection signal according to a voltage level at the connecting port.

10. The apparatus of claim 9 , wherein the detecting circuit comprises:

a capacitor device; and

a transistor, having a control terminal coupled to the connecting port, a first terminal coupled to a first voltage level of the capacitor for outputting the selection signal, and a second terminal coupled to a second voltage level.

11. An oscillating apparatus, comprising:

a biasing circuit, for dynamically adjusting a bias signal of the oscillating apparatus, comprising:

a first impedance device;

a first cascoded transistor, comprising a first transistor cascoded on a second transistor, a first terminal of the first transistor coupled to a first voltage level, a second terminal of the first transistor coupled to a first terminal of the second transistor, a second terminal of the second transistor coupled to a control terminal of the first transistor, control terminals of the first and second transistors coupled to two ends of the first impedance device, respectively;

a second cascoded transistor, comprising a third transistor cascoded on a fourth transistor, a first terminal of the third transistor coupled to the first voltage level, a second terminal of the third transistor coupled to the first terminal of the fourth transistor; and

a current mirror, comprising:

a first current path, coupled to a second terminal of the fourth transistor and a second voltage level; and

a second current path, coupled to the control terminal of the second transistor and the second voltage level;

a multi-vibrator, coupled to the biasing circuit, for generating an oscillating signal according to the biasing signal; and

a second impedance device, having two ends coupled to the second current path and the second voltage level respectively, for controlling a frequency of the oscillating signal.

12. The apparatus of claim 11 , wherein the biasing circuit and the multi-vibrator are positioned in a chip, and the second impedance device is positioned off the chip.

13. An oscillating apparatus, comprising:

a biasing circuit, for dynamically adjusting a bias signal of the oscillating apparatus, comprising:

a first impedance device;

a first cascoded transistor, comprising a first transistor cascoded on a second transistor, a first terminal of the first transistor coupled to a first voltage level, a second terminal of the first transistor coupled to a first terminal of the second transistor, a second terminal of the second transistor coupled to a control terminal of the first transistor, control terminals of the first and second transistors coupled to two ends of the first impedance device, respectively;

a second cascoded transistor, comprising a third transistor cascoded on a fourth transistor, a first terminal of the third transistor coupled to the first voltage level, a second terminal of the third transistor coupled to the first terminal of the fourth transistor;

a current mirror, comprising:

a first current path, coupled to a second terminal of the fourth transistor and a second voltage level; and

a second current path, coupled to the control terminal of the second transistor and the second voltage level; and

a capacitor device, having two ends coupled to the first current path and the second terminal of the first transistor, for avoiding the biasing circuit from oscillating;

a multi-vibrator, coupled to the biasing circuit, for generating an oscillating signal according to the biasing signal; and

a second impedance device, having two ends coupled to the second current path and the second voltage level respectively, for controlling a frequency of the oscillating signal.