SOI CMOS Schmitt trigger circuits with controllable hysteresis

• US 6,441,663 B1
• Filed: 11/02/2000
• Issued: 08/27/2002
• Est. Priority Date: 11/02/2000
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kuang, Jente Benedict, Chuang, Ching-Te Kent
• Primary Examiner(s): TRAN, TOAN V
• Application Number:
  US09/704,436
• Time in Patent Office: 663 Days
• Field of Search: 327/205, 327/206, 327/534, 327/537
• US Class Current: 327/206
• CPC Class Codes: H03K 3/3565 Bistables with hysteresis, e.g. Schmitt trigger

Abstract

A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis and a method are provided for adapting a CMOS Schmitt trigger circuit for deep sub-micrometer partially depleted SOI (PD/SOI) applications. A SOI CMOS Schmitt trigger circuit with controllable hysteresis includes a stack of a plurality of field effect transistors (FETs) connected in series between a voltage supply and ground. An input is applied to a gate of each of the stack of the plurality of field effect transistors (FETs). The stack of the plurality of field effect transistors (FETs) provides an output at a junction of a predetermined pair of the plurality of field effect transistors (FETs). At least one feedback field effect transistor (FET) has a source coupled a junction of a predefined pair of the stack of field effect transistors (FETs) and has a gate coupled to the output. A FET body of each of the stack of the plurality of field effect transistors (FETs) is connected to a voltage supply rail. The stack of the plurality of field effect transistors (FETs) includes a plurality of P-channel field effect transistors (PFETs) and a plurality of N-channel field effect transistors (NFETs). The FET body of each of the plurality of P-channel field effect transistors (PFETs) is connected to a positive voltage supply rail and the FET body of each of the plurality of N-channel field effect transistors (NFETs) is connected to a voltage supply ground rail. The FET body of a P-channel feedback field effect transistor (PFET) is connected to one of a positive voltage supply rail, the gate or the source of the feedback PFET. The FET body of a N-channel feedback field effect transistor (NFET) is connected to one of a voltage supply ground rail, the gate or the source of the feedback NFET. A successive switching threshold adjustment technique is provided. Additional successive switching threshold adjustment is achieved by successive tapping of NFET or PFET feedback devices for the V⁺ or the V⁻ trigger edges, respectively. With this arrangement, higher V⁺ and lower V⁻ are realized without using excessively wide NFET or PFET feedback devices.

Claims

1. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis comprising:

a stack of a plurality of field effect transistors (FETs) connected in series between a voltage supply and ground;

an input applied to a gate of each of said stack of said plurality of field effect transistors (FETs);

said stack of a plurality of field effect transistors (FETs) providing an output at a junction of a predetermined pair of said plurality of field effect transistors (FETs);

at least one feedback field effect transistor (FET), each feedback FET having a source coupled a junction of a predefined pair of said plurality of field effect transistors (FETs) and having a gate coupled to said output; and

a FET floating body of each of said stack of said plurality of field effect transistors (FETs) being connected to a voltage supply rail.

2. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis as recited in claim 1 wherein said stack of said plurality of field effect transistors (FETs) includes a plurality of P-channel field effect transistors (PFETs) and said FET floating body of each of said plurality of P-channel field effect transistors (PFETs) is connected to a positive voltage supply rail.

3. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis as recited in claim 1 wherein said stack of said plurality of field effect transistors (FETs) includes a plurality of N-channel field effect transistors (NFETs) and said FET floating body of each of said plurality of N-channel field effect transistors (NFETs) is connected to a voltage supply ground rail.

4. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis as recited in claim 1 wherein said at least one feedback field effect transistor (FET) includes at least one N-channel field effect transistor (NFET) and a FET floating body of said N-channel field effect transistor (NFET) is connected to a voltage supply ground potential.

5. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis as recited in claim 1 wherein said at least one feedback field effect transistor (FET) includes at least one N-channel field effect transistor (NFET) and a FET body of said NFET is connected to said gate of said NFET.

6. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis as recited in claim 1 wherein said at least one feedback field effect transistor (FET) includes at least one N-channel field effect transistor (NFET) and a FET body of said NFET is connected to said source of said NFET.

7. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis as recited in claim 1 wherein said at least one feedback field effect transistor (FET) includes at least one P-channel field effect transistor (PFET) and a FET floating body of said P-channel field effect transistor (PFET) is connected to a positive voltage supply potential.

8. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis as recited in claim 1 wherein said at least one feedback field effect transistor (FET) includes at least one P-channel field effect transistor (PFET) and a FET body of said P-channel field effect transistor (PFET) is connected to said gate of said PFET.

9. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis as recited in claim 1 wherein said at least one feedback field effect transistor (FET) includes at least one P-channel field effect transistor (PFET) and a FET body of said P-channel field effect transistor (PFET) is connected to said source of said PFET.

10. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis as recited in claim 1 wherein said at least one feedback field effect transistor (FET) includes a plurality of P-channel field effect transistors (PFETs) and a FET body of each said P-channel field effect transistor (PFET) is connected to one of said source or said gate of said PFET and at least one N-channel field effect transistor (NFET) and a FET body of each said N-channel field effect transistor (NFET) is connected to one of said source or said gate of said NFET.

11. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis as recited in claim 1 wherein said stack of said plurality of field effect transistors (FETs) includes a plurality of P-channel field effect transistors (PFETs) and a plurality of N-channel field effect transistors (NFETs);

said FET floating body of each of said plurality of P-channel field effect transistors (PFETs) is connected to a positive voltage supply rail and said FET floating body of each of said plurality of N-channel field effect transistors (NFETs) is connected to a voltage supply ground rail.

12. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis comprising:

a stack of a plurality of field effect transistors (FETs) connected in series between a voltage supply and ground;

an input applied to a gate of each of said stack of said plurality of field effect transistors (FETs);

said stack of a plurality of field effect transistors (FETs) providing an output at a junction of a predetermined pair of said plurality of field effect transistors (FETs);

a FET floating body of each of said stack of said plurality of field effect transistors (FETs) being connected to a voltage supply rail; and

at least one feedback field effect transistor (FET), said at least one feedback field effect transistor (FET) including a plurality of P-channel field effect transistors (PFETs), said plurality of feedback PFETs connected between a predefined pair of said plurality of field effect transistors (FETs) and said output; and

each of said plurality of feedback PFETs having a source coupled to a respective junction of a respective pair of said plurality of field effect transistors (FETs) and having a gate coupled to a respective next junction of a next successive pair of said plurality of field effect transistors (FETs);

said plurality of feedback PFETs for threshold adjustment of a V⁻

switching trip point of the SOI CMOS Schmitt trigger circuit.

13. A silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) Schmitt trigger circuit with controllable hysteresis comprising:

a stack of a plurality of field effect transistors (FETs) connected in series between a voltage supply and ground;

an input applied to a gate of each of said stack of said plurality of field effect transistors (FETs);

said stack of a plurality of field effect transistors (FETS) providing an output at a junction of a predetermined pair of said plurality of field effect transistors (FETs);

a FET floating body of each of said stack of said plurality of field effect transistors (FETs) being connected to a voltage supply rail; and

at least one feedback field effect transistor (FET), said at least one feedback field effect transistor (FET) including a plurality of N-channel field effect transistors (NFETs), said plurality of feedback NFETs connected between a junction of a predefined pair of said plurality of field effect transistors (FETs) and said output; and

each of said plurality of feedback NFETs having a gate coupled to a respective junction of a respective pair of said plurality of field effect transistors (FETs) and having a source coupled to respective next junction of a respective next successive pair of said plurality of field effect transistors (FETs);

said plurality of feedback NFETs for threshold adjustment of a V⁺ switching trip point of the SOI CMOS Schmitt trigger circuit.

14. A method for adapting a CMOS Schmitt trigger circuit for deep sub-micrometer partially depleted SOI (PD/SOI) applications, the SOI CMOS Schmitt trigger circuit including a stack of a plurality of P-channel and N-channel field effect transistors (PFETs and NFETs) connected in series between a voltage supply and ground, each receiving a gate input and providing an output between a predetermined pair of the FETs;

and at least one feedback FET having a source coupled a junction of a predefined pair of the plurality of field effect transistors (FETs) and having a gate coupled to the output, said method comprising the steps of;

connecting a FET floating body of each of the PFETS in the stack to a positive voltage supply rail; and

connecting a FET floating body of each of the NFETS in the stack to a voltage supply ground rail.

15. A method for adapting a CMOS Schmitt trigger circuit for deep sub-micrometer partially depleted SOI (PD/SOI) applications as recited in claim 14 further includes the step of connecting a FET body of said feedback FET to a gate of said feedback FET.

16. A method for adapting a CMOS Schmitt trigger circuit for deep sub-micrometer partially depleted SOI (PD/SOI) applications as recited in claim 14 further includes the step of connecting a FET body of said feedback FET to a source of said feedback FET.

17. A method for adapting a CMOS Schmitt trigger circuit for deep sub-micrometer partially depleted SOI (PD/SOI) applications as recited in claim 14 wherein the feedback FET comprises an N-channel field effect transistor (NFET) further includes the step of connecting a FET floating body of said feedback NFET to said voltage supply ground rail.

18. A method for adapting a CMOS Schmitt trigger circuit for deep sub-micrometer partially depleted SOI (PD/SOI) applications as recited in claim 14 wherein the feedback FET comprises a P-channel field effect transistor (PFET) further includes the step of connecting a FET floating body of said feedback PFET to said positive voltage supply rail.

19. A method for adapting a CMOS Schmitt trigger circuit for deep sub-micrometer partially depleted SOI (PD/SOI) applications, the SOI CMOS Schmitt trigger circuit including a stack of a plurality of P-channel and N-channel field effect transistors (PFETs and NFETs) connected in series between a voltage supply and ground, each receiving a gate input and providing an output between a predetermined pair of the FETs;

and at least one feedback FET having a source coupled a junction of a predefined pair of the plurality of field effect transistors (FETs) and having a gate coupled to the output, and wherein the at least one feedback FET comprises a plurality of feedback P-channel field effect transistors (PFETs), said method comprising the steps of;

connecting a FET body of each of the PFETS in the stack to a positive voltage supply rail;

connecting a FET body of each of the NFETS in the stack to a voltage supply ground rail;

connecting said plurality of feedback PFETs between said junction of said predefined pair of the plurality of field effect transistors (FETs) and said output; and

connecting a source of each of said plurality of feedback PFETs to a respective junction of a respective pair of said plurality of field effect transistors (FETs) and connecting a gate of each of said plurality of feedback PFETs to a respective next junction of a respective next successive pair of said plurality of field effect transistors (FETs);

said plurality of feedback PFETs for threshold adjustment of the V⁻

switching trip point of the SOI CMOS Schmitt trigger circuit.

20. A method for adapting a CMOS Schmitt trigger circuit for deep sub-micrometer partially depleted SOI (PD/SOI) applications, the SOI CMOS Schmitt trigger circuit including a stack of a plurality of P-channel and N-channel field effect transistors (PFETs and NFETs) connected in series between a voltage supply and ground, each receiving a gate input and providing an output between a predetermined pair of the FETs;

and at least one feedback FET having a source coupled a junction of a predefined pair of the plurality of field effect transistors (FETs) and having a gate coupled to the output, and wherein the at least one feedback FET comprises a plurality of feedback N-channel field effect transistors (NFETs), said method comprising the steps of;

connecting a FET body of each of the PFETS in the stack to a positive voltage supply rail;

connecting a FET body of each of the NFETS in the stack to a voltage supply ground rail;

connecting said plurality of feedback NFETs between said junction of said predefined pair of the plurality of field effect transistors (FETs) and said output; and

connecting a gate of each of said plurality of feedback NFETs to a respective junction of a respective pair of said plurality of field effect transistors (FETs) and connecting a source of each of said plurality of feedback PFETs to a respective next junction of a respective next successive pair of said plurality of field effect transistors (FETs);

said plurality of feedback NFETs for threshold adjustment of the V⁺ switching trip point of the SOI CMOS Schmitt trigger circuit.