Auto-range current mirror circuit

• US 7,352,245 B2
• Filed: 06/30/2006
• Issued: 04/01/2008
• Est. Priority Date: 06/30/2006
• Status: Active Grant

• Current Assignee: Silicon Touch Technology Inc.
• Original Assignee: Silicon Touch Technology Inc.
• Inventors: Shih, Fu-Yang, Chin, Hsu-Yuan
• Primary Examiner(s): NGUYEN, PATRICIA T
• Application Number:
  US11/477,378
• Publication Number:
  US 20080001672A1
• Time in Patent Office: 641 Days
• Field of Search: 330/288, 330/257, 330/310
• US Class Current: 330/288
• CPC Class Codes: G05F 3/262 using field-effect transistors only
• CPC Class Codes: H03F 2200/249 A switch coupled in the input circuit of an amplifier being controlled by a circuit, e.g. feedback circuitry being controlling the switch
• CPC Class Codes: H03F 2200/366 Multiple MOSFETs are coupled in parallel
• CPC Class Codes: H03F 2200/421 Multiple switches coupled in the output circuit of an amplifier are controlled by a circuit
• CPC Class Codes: H03F 2200/462 the current being sensed
• CPC Class Codes: H03F 2200/78 A comparator being used in a controlling circuit of an amplifier
• CPC Class Codes: H03F 2200/91 the amplifier has a current mode topology
• CPC Class Codes: H03F 2203/7215 the gated amplifier being switched on or off by a switch at the input of the amplifier
• CPC Class Codes: H03F 2203/7221 the gated amplifier being switched on or off by a switch at the output of the amplifier
• CPC Class Codes: H03F 2203/7236 the gated amplifier being switched on or off by putting into parallel or not, by choosing between amplifiers by (a ) switch(es)
• CPC Class Codes: H03F 3/345 with field-effect devices H03F3/347 takes precedence
• CPC Class Codes: H03F 3/72 Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal

Abstract

An auto-range current mirror circuit has a current sensing circuit, a front and rear stage current mirrors each has an adjustable amplifying rate. The current sensing circuit presets a threshold current and has an input current of the front stage current mirror. The current sensing current compares the input current with a threshold current and then outputs a controlling signal to the front and rear stage current mirrors to adjust a suitable amplifying rate. Therefore, a bias current of the rear stage current mirror is amplified by the suitable amplifying rate to improve the quality of output current of the rear stage current mirror.

Claims

1. An auto-range current mirror circuit comprising:

a front stage current mirror having a first adjustable amplifying rate, a current input adapted to connect to an input current and a current output, and generating a bias current in the current output;

a rear stage current mirror

having a second adjustable amplifying rate, an input terminal connected to the current output of the front stage current mirror and at least one output terminal,

connected to the front stage current mirror in series to have the bias current from the front stage current mirror, and

amplifying the bias current by the second amplifying rate to generate an output current in the output terminal; and

at least one current sensing circuit, each electronically connects to the front and rear stage current mirrors and the input current and has a preset threshold current, wherein each current sensing circuit outputs a controlling signal to the front and rear stage current mirrors to adjust a suitable amplifying rate according to the present input current.

2. The current mirror circuit as claimed in claim 1 further comprising multiple current sensing circuits respectively having different preset threshold currents.

3. The current mirror circuit as claimed in claim 1 further comprising at least one middle stage current mirror connected between the front stage and the rear stage current mirrors in series.

4. The current mirror circuit as claimed in claim 3, wherein each middle stage current mirror comprises

at least one front stage current mirror unit connected to the rear stage current mirror;

and

at least one rear stage current mirror unit connected to the front stage current mirror, and each rear stage current mirror unit provides an output current.

5. The current mirror circuit as claimed in claim 1, wherein the current sensing circuit comprises:

a voltage converter connected to the current input of the front stage current mirror to convert the input current to a corresponding voltage and having

an input terminal connected to the current input of the front stage current mirror; and

an output terminal outputting the corresponding voltage; and

a voltage comparator having

a first input connected to output terminal of the voltage converter;

a second input connected to a reference voltage; and

an output electronically connected to the front and rear stage current mirrors to generate a voltage by comparing the reference voltage with the converted voltage corresponding to the input current.

6. The current mirror circuit as claimed in claim 1, wherein the current sensing circuit comprises a current comparator having

two inputs respectively connected to the current input of the front stage current mirror and a reference current;

and

an output electronically connected to the front and rear stage current mirrors to generate a current by comparing the reference current with the input current.

7. The current mirror circuit as claimed in claim 1, wherein the front stage and the rear stage current mirrors respectively comprise

a basic two-transistor current source connected to the input current and generate the output current;

at least one additional transistor connected to the basic two-transistor current source in parallel; and

at least one switch connected between the corresponding additional transistor and the basic two-transistor current mirror to determine whether the corresponding additional transistor electronically connected to the basic two-transistor current source to adjust a amplifying rate of the front and rear stage current mirrors.

8. The current mirror circuit as claimed in claim 1, wherein the front stage current mirror comprises:

a basic two-transistor current source connected to the input current and generate the output current;

at least one additional transistor connected to the basic two-transistor current source in parallel and the current input; and

at least one switch connected between the corresponding additional transistor and the basic two-transistor current mirror to determine whether the corresponding additional transistor electronically connected to the basic two-transistor current source to adjust an amplifying rate of the front stage current mirror.

9. The current mirror circuit as claimed in claim 1, wherein the front stage current mirror comprises

a basic two-transistor current source connected to the input current and generate the output current;

at least one additional transistor connected to the basic two-transistor current source in parallel and the current output; and

at least one switch connected between the corresponding additional transistor and the basic two-transistor current mirror to determine whether the corresponding additional transistor electronically connected to the basic two-transistor current source to adjust an amplifying rate of the front stage current mirror.

10. The current mirror circuit as claimed in claim 1, wherein the front stage current mirror comprises

a basic two-transistor current source connected to the input current and generate the output current;

two additional transistor respectively connected to the current input and basic two-transistor current source in parallel, and the current output and the basic two-transistor current source in parallel; and

two switches, each connects between the corresponding additional transistor and the basic two-transistor current mirror to determine whether the corresponding additional transistor electronically connected to the basic two-transistor current source to adjust an amplifying rate of the front stage current mirror.

11. The current mirror circuit as claimed in claim 1, wherein the rear stage current mirror comprises

a basic two-transistor current source connected to the input current and generate the at least one output current;

at least one additional transistor connected to the basic two-transistor current source in parallel and the input terminal; and

at least one switch connected between the corresponding additional transistor and the basic two-transistor current source to determine whether the corresponding additional transistor electronically connected to the basic two-transistor current source to adjust an amplifying rate of the rear stage current mirror.

12. The current mirror circuit as claimed in claim 1, wherein the rear stage current mirror comprises

a basic two-transistor current source connected to the input current and generate the at least one output current;

at least one additional transistor connected to the basic two-transistor current source in parallel and the corresponding output terminal; and

at least one switch connected between the corresponding additional transistor and the basic two-transistor current mirror to determine whether the corresponding additional transistor electronically connected to the basic two-transistor current source to adjust an amplifying rate of the rear stage current mirror.

13. The current mirror circuit as claimed in claim 1, wherein the rear stage current mirror comprises

a basic two-transistor current source connected to the input current and generate the at least one output current;

two additional transistor respectively connected to the input terminal and basic two-transistor current source in parallel, and the output terminal and the basic two-transistor current source in parallel; and

two switches each connects between the corresponding additional transistor and the basic two-transistor current mirror to determine whether the corresponding additional transistor electronically connected to the basic two-transistor current source to adjust an amplifying rate of the rear stage current mirror.

14. The current mirror circuit as claimed in claim 7, each additional transistor is MOS transistor having a drain terminal, source terminal and a gate terminal.

15. The current mirror circuit as claimed in claim 14, each switch is connected to the drain terminal.

16. The current mirror circuit as claimed in claim 14, each switch is connected to the drain terminal, the source terminal and the gate terminal.