Voltage reference generation circuit and power source incorporating such circuit

• US 6,552,603 B2
• Filed: 06/21/2001
• Issued: 04/22/2003
• Est. Priority Date: 06/23/2000
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Ueda, Yoshinori
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): ENGLUND, TERRY LEE
• Application Number:
  US09/884,922
• Publication Number:
  US 20020036488A1
• Time in Patent Office: 670 Days
• Field of Search: 327/538, 327/540, 327/541, 327/542, 327/543, 323/312, 323/313
• US Class Current: 327/541
• CPC Class Codes: G05F 3/24 wherein the transistors are of the field-effect type only G05F3/205, G05F3/26, G05F3/30 take precedence

Abstract

A voltage reference generation circuit is disclosed including a voltage reference generating stage and a voltage reference output stage, in which a depletion-mode MOS transistor and an enhancement-mode MOS transistor are connected in series, and the junction formed between these MOS transistors serves as an output terminal for outputting a voltage to be input to the voltage reference output stage. In the output stage, two enhancement-mode MOS transistors having the same channel dopant profile are connected in series between a power source and the ground, the gate of one MOS transistor is connected to the output terminal of the generating stage, the gate and drain of the other MOS transistor are interconnected, and the junction formed between these MOS transistors serves as an output terminal for a voltage reference. In addition, each of the enhancement-mode MOS transistors is provided with a floating gate having a different threshold voltage depending on, the coupling coefficient between the floating gate and a gate, the amount of charge input to the floating gate, the kind of dielectric material included in the gate, or the thickness of a gate oxide layer, which is suitably utilized to supply reference voltages with improved stability to fluctuations in operating temperatures or processing parameters.

Claims

1. A voltage reference generation circuit comprising:

a depletion-mode MOS transistor having a gate and a drain interconnected to serve as a constant current source;

at least two enhancement-mode MOS transistors connected in series to said depletion-mode MOS transistor and operating at a saturated drain voltage by the constant current supplied by said depletion-mode MOS transistor;

a first output terminal comprising a first junction of said at least two enhancement-mode MOS transistors; and

a second output terminal comprising a second junction of one of said at least two enhancement-mode MOS transistors and said depletion-mode MOS transistor;

wherein said at least two enhancement-mode MOS transistors have a same channel dopant profile and different threshold voltages.

2. The voltage reference generation circuit according to claim 1, wherein said at least two enhancement-mode MOS transistors include two MOS transistors having interconnected gates and a junction of said two enhancement-mode MOS transistors serves as said first output terminal.

3. The voltage reference generation circuit according to claim 1, wherein a gate of each of said enhancement-mode MOS transistors are interconnected.

4. The voltage reference generation circuit according to claim 1, wherein each of said enhancement-mode MOS transistors is provided with a floating gate to have a different threshold voltage depending on a coupling coefficient between said floating gate and a control gate.

5. The voltage reference generation circuit according to claim 1, wherein each of said enhancement-mode MOS transistors is provided with a floating gate to have a different threshold voltage depending on an amount of charge input to said floating gate.

6. The voltage reference generation circuit according to claim 1, wherein each of said enhancement-mode MOS transistors includes a floating gate and has a different threshold voltage depending on a kind of dielectric material included in said floating gate.

7. The voltage reference generation circuit according to claim 1, wherein each of said enhancement-mode MOS transistors has a floating gate and a different threshold voltage depending on a thickness of a gate oxide layer included in said floating gate.

8. A power source comprising:

a voltage reference generation circuit, said voltage reference generation circuit comprising,

a depletion-mode MOS transistor having a gate and a drain configured to serve as a constant current source;

at least two enhancement-mode MOS transistors connected in series to said depletion-mode MOS transistor and operating at a saturated drain voltage by the constant current supplied by said depletion-mode MOS transistor;

a first output terminal comprising a first junction of said at least two enhancement-mode MOS transistors; and

a second output terminal comprising a second junction of one of said at least two enhancement-mode MOS transistors and said depletion-mode MOS transistor;

wherein said at least two enhancement-mode MOS transistors have a same channel dopant profile and different threshold voltages; and

a detection circuit configured to compare a voltage supplied thereto to a reference voltage between said first and second output terminals of said voltage reference generation circuit.

9. A voltage reference generation circuit comprising:

a depletion-mode MOS transistor means having a gate and a drain interconnected to serve as a constant current source;

at least two enhancement-mode MOS transistor means connected in series to said depletion-mode MOS transistor and operating at a saturated drain voltage by the constant current supplied by said depletion-mode MOS transistor;

a first output terminal comprising a junction of said at least two enhancement-mode MOS transistor means; and

a second output terminal comprising a junction of said depletion-mode MOS transistor means and said at least two enhancement-mode MOS transistor means;

wherein said at least two enhancement-mode MOS transistor means have a same channel dopant profile and different threshold voltages.

10. The voltage reference generation circuit according to claim 9, wherein said at least two enhancement-mode MOS transistor means include two MOS transistor means having interconnected gates, and a junction of said two MOS transistor means serves as said first output terminal.

11. The voltage reference generation circuit according to claim 9, wherein a gate of each of said enhancement-mode MOS transistor means are interconnected.

12. The voltage reference generation circuit according to claim 9, wherein each of said enhancement-mode MOS transistor means is provided with a floating gate to have a different threshold voltage depending on a coupling coefficient between said floating gate and a control gate.

13. The voltage reference generation circuit according to claim 9, wherein each of said enhancement-mode MOS transistor means is provided with a floating gate to have a different threshold voltage depending on an amount of charge input to said floating gate.

14. The voltage reference generation circuit according to claim 9, wherein each of said enhancement-mode MOS transistor means includes a floating gate and has a different threshold voltage depending on a kind of dielectric material included in said floating gate.

15. The voltage reference generation circuit according to claim 9, wherein each of said enhancement-mode MOS transistor means includes a floating gate and a different threshold voltage depending on a thickness of a gate oxide layer included in said floating gate.

16. A power source comprising:

voltage reference generation circuit means, said voltage reference generation circuit means comprising,

a depletion-mode MOS transistor having a gate and a drain interconnected to serve as a constant current source;

at least two enhancement-mode MOS transistors connected in series to said depletion-mode MOS transistor and operating at a saturated drain voltage by the constant current supplied by said depletion-mode MOS transistor;

a first output terminal comprising a junction of said at least two enhancement-mode MOS transistors; and

a second output terminal comprising a junction of said depletion-mode MOS transistor and one of said at least two enhancement-mode MOS transistors;

wherein said at least two enhancement-mode MOS transistors having a same channel dopant profile and a different threshold voltage; and

detection circuit means for comparing a voltage supplied thereto to a reference voltage between said first and second output terminals of said voltage reference generation circuit means.