High-speed current switch circuit

• US 20050280457A1
• Filed: 08/26/2005
• Published: 12/22/2005
• Est. Priority Date: 12/21/2000
• Status: Active Grant

• Current Assignee: Asahi Kasei Microsystems Co., Ltd. (Asahi Kasei Corporation)
• Original Assignee: Asahi Kasei Microsystems Co., Ltd. (Asahi Kasei Corporation)
• Inventors: Ikeda, Masaki, Fujita, Takeshi, Aiba, Yusuke, Hirose, Hideaki, Maruo, Akio
• Granted Patent: US 7,332,944 B2
• Time in Patent Office: Days
• US Class Current: 327/170
• CPC Class Codes: G11B 7/126 Circuits, methods or arrangements for laser control or stabilisation
• CPC Class Codes: H03K 17/04123 in field-effect transistor switches
• CPC Class Codes: H03K 17/6872 using complementary field-effect transistors
• CPC Class Codes: H03L 7/02 using a frequency discriminator comprising a passive frequency-determining element

Abstract

A high-speed current switch circuit of this invention has an n-type MOS transistor Q11 which switches and outputs a current, and a control circuit 11 which performs switching control of the MOS transistor Q11. In the control circuit 11, a source follower is formed by an N-type MOS transistor Q12 and a constant current source I2 which is a load on this transistor. A switch SW11 is connected to the MOS transistor Q12 to perform switching control of a current flowing through the MOS transistor Q12. The control circuit 11 includes a switch SW12 capable of grounding the gate of the MOS transistor 11. The source of the MOS transistor Q12 is connected to the gate of the MOS transistor Q11. Thus, even if a large current is caused to flow through the output transistor, the output transistor can be made to operate for switching at a high speed.

Claims

1-12. -12. (canceled)

13. An oscillator, characterized by comprising:

oscillation means in which the oscillation frequency is controlled on the basis of a current or voltage externally supplied;

a constant current source circuit;

charge means which charges a capacitor with a constant current from said constant current source circuit on the basis of an oscillation output from said oscillation means; and

control means which generates the current or voltage for control of the oscillation frequency of said oscillation means on the basis of electric charge stored in said capacitor and a predetermined reference value.

14. The oscillator according to claim 13, characterized in that said constant current source circuit generates the constant current on the basis of a bandgap voltage.

15. The oscillator according to claim 13 or 14, characterized in that said control means includes an integrator formed of an operational amplifier and an integrating capacitor;

said integrator performs integration on the basis of the charged voltage across said capacitor and the predetermined reference value; and

the current or voltage for control of the oscillation frequency of said oscillation means is generated on the basis of an integrated output from said integrator.

16. The oscillator according to claim 15, characterized in that said oscillation means comprises a current-controlled oscillator;

said control means includes a voltage-current conversion circuit which converts the output from said integrator into a current; and

an output current from said voltage-current conversion circuit is supplied to said current-controlled oscillator.

17. The oscillator according to claim 13, characterized in that said constant current source circuit is arranged so that the constant current generated therein is variable according to the value of a resistance, and the oscillation frequency of said oscillation means is changed on the basis of change of said value of the resistance.

18. The oscillator according to claim 13, characterized in that a frequency divider which divides the frequency of the oscillation output from said oscillation means is interposed between said oscillation means and said control means.

19. The oscillator according to claim 18, characterized in that said frequency divider is arranged so that its division ratio is variable, and the oscillation frequency is changed on the basis of the division ratio.

20-22. -22. (canceled)