SOI CMOS dynamic circuits having threshold voltage control

• US 6,433,587 B1
• Filed: 03/17/2000
• Issued: 08/13/2002
• Est. Priority Date: 03/17/2000
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Smeys, Peter, Bernstein, Kerry, Hargrove, Michael J., Assaderaghi, Fariborz, Rohrer, Norman J.
• Primary Examiner(s): Tokar, Michael
• Assistant Examiner(s): TRAN, ANH Q
• Application Number:
  US09/528,207
• Time in Patent Office: 879 Days
• Field of Search: 326/93-98
• US Class Current: 326/95
• CPC Class Codes: H03K 19/00361 in field effect transistor circuits
• CPC Class Codes: H03K 19/096 Synchronous circuits, i.e. using clock signals H03K19/01728, H03K19/01855 take precedence

Abstract

A circuit for maintaining the threshold voltages of transistors implemented in a dynamic CMOS circuit. A plurality of transistors have source drain connections connected between the body contacts of transistors in the dynamic CMOS circuits, and the constant voltage potential. When operating the dynamic CMOS circuit in the precharge phase, the body of each of the CMOS circuit transistors is maintained at the constant voltage potential. During the evaluate phase, the body potential is permitted to float to its precharge state. The initial reference level voltage established during a precharge phase maintains the transistor gate-source threshold voltage at a constant value, eliminating both bipolar effects and history effects which accompanying a changing body potential.

Claims

1. A logic circuit formed in an SOI type substrate and having a first input for receiving an evaluate signal and a plurality of logic inputs for receiving signals to be logically evaluated, comprising:

circuitry formed in the SOI type substrate and coupled to a body of at least one internal FET of the logic circuit and also coupled to a voltage terminal;

said circuit having a second input for receiving a clock signal having at least two alternating voltage levels, the second input coupled to the circuitry for effectuating a temporary pull down of the voltage level of the body in response to one of the clocks signal'"'"'s voltage levels; and

wherein the voltage level of the body is pulled to the voltage terminal level just prior to an evaluate phase of logic circuit.

2. The circuit of claim 1, wherein the circuitry allows the voltage level of the body to float in response to a second one of the clock signal'"'"'s voltage levels.

3. The circuit of claim 2, wherein the clock signal is a complement of the evaluate signal.

4. The circuit of claim 1, wherein the circuitry comprises only a single control FET for each said internal FET to which the circuitry is coupled.

5. A dynamic CMOS circuit having transistors coupled to a charged node which control the voltage potential on the charged node representing a result of a logic operation, further comprising:

a plurality of switching transistors serially connecting the body of each transistor which is connected to said node to a reference potential voltage; and

means for enabling said switching transistors during a precharge phase of said dynamic CMOS circuit whereby said body is established at a potential substantially equal to said reference potential.

6. The dynamic CMOS circuit according to claim 5, wherein said reference potential is lower than a precharge potential applied to said charge node.

7. The dynamic CMOS circuit according to claim 5, wherein said means for enabling said switching transistors provides a signal to a gate of said switching transistor switch is substantially a complement of a clocking signal applied to said CMOS circuit.

8. A dynamic CMOS circuit forming charged nodes with transistors which have a controlled threshold value comprising:

a first transistor having a drain connected to a voltage source Vcc, and a gate connected to a source of clock signals;

a second transistor serially connected with a source of said first transistor, forming node which can be charged to a voltage level Vcc when a clock pulse enables said first transistor to conduct;

a third transistor connected with said second transistor and to a common terminal of said voltage source Vcc; and

a fourth transistor having a source drain connected to a body contact of said second transistor and to a terminal of a second voltage supply, and having a gate connection connected to a source of pulses which enable said fourth transistor to conduct when said first transistor is conducting to apply a voltage to said second transistor body which prevents lowering of said second transistor threshold voltage.

9. The dynamic CMOS circuit according to claim 8 wherein said pulses applied to said fourth transistor are the complement of said clock pulses applied to said first transistor.

10. The dynamic CMOS circuit according to claim 8 further comprising:

a fifth transistor having a drain source connection connected in parallel with said second transistor drain source connection, said fifth transistor gate connection being connected to receive a logic signal; and

a sixth transistor having a drain source connection connected between a body contact on said fifth transistor and said second voltage supply, and having a gate connection connected to said source of pulses.

11. The circuit according to claim 8, further comprising:

a pull up transistor connected to said node and said voltage source Vcc and;

an inverter circuit connected to said node and a gate of said pull up transistor.

12. A circuit for maintaining the threshold voltage for transistors which form charged nodes in a dynamic CMOS circuit comprising:

a plurality of transistors which have source drain connections connected between the body contacts of said transistors forming said charged nodes and a reference voltage, said transistors having a gate connection which is enabled during charging of said nodes of pulses which are complementary to clock pulses which enables charging of said nodes whereby said body contacts are maintained at a voltage which maintains said threshold voltages constant.