Cascode circuit and semiconductor device

• US 7,479,821 B2
• Filed: 03/16/2007
• Issued: 01/20/2009
• Est. Priority Date: 03/27/2006
• Status: Active Grant

• Current Assignee: Ablic Inc. (Minebea Mitsumi, Inc.)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Imura, Takashi
• Primary Examiner(s): Richards; N. Drew
• Assistant Examiner(s): Houston; Adam
• Application Number:
  US11/724,940
• Publication Number:
  US 20070221996A1
• Time in Patent Office: 676 Days
• Field of Search: 327/538, 327/541, 327/543, 323/315
• US Class Current: 327/538
• CPC Class Codes: G05F 3/24 wherein the transistors are of the field-effect type only G05F3/205, G05F3/26, G05F3/30 take precedence
• CPC Class Codes: H01L 27/0883 Combination of depletion and enhancement field effect transistors
• CPC Class Codes: H03F 3/345 with field-effect devices H03F3/347 takes precedence

Abstract

A reference voltage circuit having a high power supply rejection ratio, and can operate at low voltage is provided. The reference voltage circuit includes a bias circuit constructed such that a depletion type transistor (3) is connected in series to a power supply voltage supply terminal of a load circuit, an enhancement type MOS transistor (4) for detecting current through the load circuit to operate as a current source is connected to the load circuit, a depletion type MOS transistor (5) is connected in series to the transistor (4), and a gate terminal of the transistor (5) is connected to a source terminal of the transistor (5), in which the gate terminal of the depletion type transistor (3) is connected to the source terminal of the depletion type transistor (5).

Claims

1. A cascode circuit comprising:

a first N-channel depletion type MOS transistor having a source and a gate connected to each other;

a second N-channel depletion type MOS transistor having a gate connected to the gate of the first N-channel depletion type MOS transistor, for supplying power to a load circuit connected to a source of the second N-channel depletion type MOS transistor; and

a control current source connected to the source of the first N-channel depletion type MOS transistor, the control current source being controlled by current through the load circuit, wherein

the drain-source voltage of the first N-channel depletion type MOS transistor is set to be higher than threshold voltage, and the substrate potential is set to be lower than source potential of the first N-channel depletion type MOS transistor, and

the drain-source voltage of the second N-channel depletion type MOS transistor is set to be higher than threshold voltage, and the substrate potential is set to be lower than source potential of the second N-channel depletion type MOS transistor.

2. A cascode circuit according to claim 1, wherein the substrate potential of the first N-channel depletion type MOS transistor and the substrate potential of the second N-channel depletion type MOS transistor are grounded.

3. A cascode circuit according to claim 1, wherein the control current source comprises a first N-channel enhancement type MOS transistor having a gate connected to the load circuit and having a drain connected to the source of the first N-channel depletion type MOS transistor.

4. A semiconductor device comprising the cascode circuit according to claim 3, wherein the load circuit is a reference voltage circuit comprising:

a third N-channel depletion type MOS transistor having a drain connected to the source of the second N-channel depletion type MOS transistor and having a source and a gate connected to the gate of the first N-channel enhancement type type MOS transistor; and

a second N-channel enhancement type MOS transistor having a drain and a gate connected to the source of the third N-channel depletion type MOS transistor.

5. A semiconductor device comprising the cascode circuit according to claim 3, wherein the load circuit is a source follower circuit comprising:

a third N-channel enhancement type MOS transistor having a drain connected to the source of the second N-channel depletion type MOS transistor; and

a second N-channel enhancement type MOS transistor having a drain and a gate connected to the source of the third N-channel enhancement type MOS transistor and to the gate of the first N-channel enhancement type MOS transistor.

6. A semiconductor device according to claim 4, wherein the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor.

7. A semiconductor device according to claim 4, wherein the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor.

8. A semiconductor device according to claim 4, wherein

the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor, and

the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor.

9. A semiconductor device according to claim 5, wherein the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor.

10. A semiconductor device according to claim 5, wherein the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor.

11. A semiconductor device according to claim 5, wherein

the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor, and

the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor.

12. A semiconductor device comprising a cascode circuit, the cascode circuit comprising:

a first N-channel depletion type MOS transistor having a source and a gate connected to each other;

a second N-channel depletion type MOS transistor having a gate connected to the gate of the first N-channel depletion type MOS transistor;

a third N-channel depletion type MOS transistor having a drain connected to a source of the second N-channel depletion type MOS transistor, and having a source and a gate connected to each other;

a second N-channel enhancement type MOS transistor having a drain connected to the source of the third N-channel depletion type MOS transistor;

a first N-channel enhancement type MOS transistor having a drain connected to the source of the first N-channel depletion type MOS transistor;

a fourth N-channel depletion type MOS transistor having a gate connected to the gate of the first N-channel depletion type MOS transistor;

a fifth N-channel depletion type MOS transistor having a drain connected to a source of the fourth N-channel depletion type MOS transistor, and having a gate connected to the source of the third N-channel depletion type MOS transistor; and

a plurality of serially connected resistances connected to the gates of the first and second N-channel enhancement type MOS transistors and to a source of the fifth N-channel depletion type MOS transistor, wherein

the cascode circuit is constructed such that positive constant voltage is output from an arbitrary point of connection of the plurality of serially connected resistances, and

substrate potentials of all the MOS transistors are grounded.

13. A semiconductor device according to claim 12, wherein the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor.

14. A semiconductor device according to claim 12, wherein the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor.

15. A semiconductor device according to claim 12, wherein

the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor, and

the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor.

16. A semiconductor device comprising a cascode circuit, the cascode circuit comprising:

a first N-channel depletion type MOS transistor having a source and a gate connected to each other;

a second N-channel depletion type MOS transistor having a gate connected to the gate of the first N-channel depletion type MOS transistor;

a third N-channel depletion type MOS transistor having a drain connected to a source of the second N-channel depletion type MOS transistor, and having a source and a gate connected to each other;

a second N-channel enhancement type MOS transistor having a drain connected to the source of the third N-channel depletion type MOS transistor;

a first N-channel enhancement type MOS transistor having a drain connected to the source of the first N-channel depletion type MOS transistor;

a fourth N-channel depletion type MOS transistor having a gate connected to the gate of the second N-channel depletion type MOS transistor;

a fifth N-channel depletion type MOS transistor having a drain connected to a source of the fourth N-channel depletion type MOS transistor, and having a gate connected to the source of the third N-channel depletion type MOS transistor; and

a plurality of serially connected resistances connected to the gates of the first and second N-channel enhancement type MOS transistors and to a source of the fifth N-channel depletion type MOS transistor, wherein

the cascode circuit is constructed such that positive constant voltage is output from an arbitrary point of connection of the plurality of serially connected resistances, and

substrate potentials of all the MOS transistors are grounded.

17. A semiconductor device according to claim 16, wherein the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor.

18. A semiconductor device according to claim 16, wherein the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor.

19. A semiconductor device according to claim 16, wherein

the transconductance coefficient of the first N-channel enhancement type MOS transistor is made larger than the transconductance coefficient of the second N-channel enhancement type MOS transistor, and

the transconductance coefficient of the first N-channel depletion type MOS transistor is made smaller than the transconductance coefficient of the second N-channel depletion type MOS transistor.