Simultaneous dual rail static carry-save-adder circuit using silicon on insulator technology

• US 6,785,703 B2
• Filed: 05/24/2001
• Issued: 08/31/2004
• Est. Priority Date: 05/24/2001
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Philhower, Robert Alan, Bradley, Douglas Hooker, Cao, Tai Anh
• Primary Examiner(s): Mai, Tan V.
• Application Number:
  US09/864,137
• Publication Number:
  US 20030005017A1
• Time in Patent Office: 1,195 Days
• Field of Search: 708/700, 708/702, 326/52-55
• US Class Current: 708/702
• CPC Class Codes: G06F 7/5016 forming at least one of the output signals directly from the minterms of the input signals, i.e. with a minimum number of gate levels

Abstract

An adder circuit is provided that generates the sum and sum complement (sum_) signals by constructing the logic in such a way that various levels of both N-type devices and P-type devices are both “on” at the same when that leg is to be open. The logic is then determined by another level and only one P or N type device is on at a given time. For carry and carry complement (carry_) signals a circuit is provided that is symmetrical with respect to P and N devices. The carry and carry_ signals are generated by inputting the complement signals to the same circuit used to generate the carry signal. The symmetrical P and N type devices are complementary in that associated devices are on or off with respect to each other. Both the carry and carry_ signals are concurrently output. The symmetric nature of the static, dual rail, simultaneous, sum and carry circuits will improve switching performance and minimize the floating body effect that can be found in silicon on insulator (SOI) devices.

Claims

1. A static summing circuit for generating an arithmetic output, comprising:

a first set of P type and N type transistor devices symmetrically connected to one another such that each said P type transistor has a corresponding N type transistor; and

a second set of P type and N type transistor devices, symmetrically connected to one another such that each said P type transistor has a corresponding N type transistor said first set of devices and said second set of devices being formed on an insulating layer which introduces a floating body effect caused by said insulating layer wherein a varying voltage drop occurs across said first set of devices and said second set of devices;

wherein said arithmetic output and a complement thereof are provided concurrently on respective output nodes of said circuit;

wherein each of said P type transistors and said corresponding N type transistors in said first set of devices are concurrently in either a turned on or turned off state and each of said P type transistors and said corresponding N type transistors in said second set of devices are concurrently in either a turned on or turned off state, such that said floating body effect is minimized.

2. A circuit according to claim 1 wherein said circuit includes a third set of devices including both N type transistors and P type transistors.

3. A circuit according to claim 2 wherein each of said N type transistors in said third set of devices is associated with a corresponding P type transistor in said third set of devices.

4. A circuit according to claim 3 wherein each of said N type transistors in said third set of devices is off when said associated corresponding P type transistor in said third set of devices is turned on.

5. A circuit according to claim 4 wherein each of the P type transistors in said third set of devices is off when said associated corresponding N type transistor in said third set of devices is turned on.

6. A data processing system, comprising:

a memory;

a central processing unit;

at least one execution unit included within said central processing unit for performing arithmetic and logical operations;

an arithmetic circuit within said at least one execution unit which performs arithmetic operations on data stored in said memory;

at least one adder circuit included in said arithmetic circuit that receives plural input signals and generates a sum thereof;

wherein said at least one adder includes a static circuit for generating an arithmetic output, including;

a first set of P type and N type transistor devices;

a second set of P type and N type transistor devices, having a second switching characteristic, symmetrically connected to one another such that each said P type transistor has a corresponding N type transistor said first set of devices and said second set of devices being formed on an insulating layer which introduces a floating body effect caused by said insulating layer wherein a varying voltage drop occurs across said first set of devices and said second set of devices such that said output and a complement thereof are provided concurrently on respective output nodes of said circuit;

wherein each of said P type transistors and said corresponding N type transistors in said first set of devices are concurrently in either a turned on or turned off state and each of said P type transistors and said corresponding N type transistors in said second set of devices are concurrently in either a turned on or turned off state, such that said floating body effect is minimized.

7. A system according to claim 6 wherein said circuit includes a third set of device having both N type and P type transistors.

8. A system according to claim 7 wherein each of the N type transistors in said third set of devices is associated with a corresponding P type transistor in said third set of devices.

9. A system according to claim 8 wherein said N type transistors in said third set of devices is off when said associated corresponding P type transistor in said third set of devices is turned on and the P type transistors in said third set of devices are off when said associated corresponding N type transistor in said third set of devices is turned on.

10. A method of generating an arithmetic output from a static summing circuits, said method comprising the steps of:

providing a first set of P type and N type transistor devices symmetrically connected to one another such that each said P type transistor has a corresponding N type transistor; and

symmetrically connecting a second set of P type and N type transistor devices, to one another such that each said P type transistor has a corresponding N type transistor wherein said first set of devices and said second set of devices are formed on an insulating layer which introduces a floating body effect caused by said insulating layer wherein a varying voltage drop occurs across said first set of devices and said second set of devices;

wherein said arithmetic output and a complement thereof are provided concurrently on respective output nodes of said circuit; and

wherein each of said P type transistors and said corresponding N type transistors in said first set of devices are concurrently in either a turned on or turned off state and each of said P type transistors and said corresponding N type transistors in said second set of devices are concurrently in either a turned on or turned off state, such that said floating body effect is minimized.

11. A method according to claim 10, further comprising the steps of:

providing a third set of devices including both N type transistors and P type transistor; and

associating each of said N type transistor in said third set of devices with a corresponding P type transistor in said third set of devices.

12. A method according to claim 11 further comprising the step of turning off said N type transistors in said third set of devices when said corresponding P type transistor in said third set of devices is turned on.

13. A method according to claim 11, further comprising the step of turning off said P type transistors in said third set of devices when said corresponding N type transistor in said third set of devices is turned on.

14. A static circuit for generating an arithmetic output, comprising:

a first set of N type transistor devices and P type transistor devices, said N type transistor devices and said P type transistor devices in said first set being symmetrically connected to one another;

a second set of N type transistor devices and P type transistor devices, said N type transistor devices and said P type transistor devices in said second set being symmetrically connected to one another; and

a third set of N type transistor devices and P type transistor devices, said N type transistor devices and said P type transistor devices in said third set being symmetrically connected to one another;

wherein all of said N type transistor devices and said P type transistor devices in said first, second and third sets are formed on an insulating layer which introduces a floating body effect caused by said insulating layer wherein a varying voltage drop occurs across said devices in said first, second and third sets;

wherein the N type transistor devices and P type transistor devices in said first set and said second set are all in one of a turned on state or a turned off state at any given time period and wherein the N type transistor devices and P type transistor devices in said third set are in one of a turned on state or a turned off state respective to one another at any given time period to minimize said floating body effect; and

wherein said arithmetic output and a complement thereof are provided concurrently on respective output nodes of said circuit.