Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
1999-05-14
2001-08-07
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S170000, C327S112000
Reexamination Certificate
active
06271713
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to circuits and more particularly, to a dynamic threshold source follower voltage driver circuit.
2. Background Art
A driver circuit is used to provide the ability to quickly change the input voltage of a receiver circuit that it drives. Instances in which a driving circuit may be used include to drive a relatively long interconnect conductor and to drive a wide fan-out set of conductors. A commonly used driver circuit includes first and second inverters connected in series, wherein each inverter includes a pull-up p-channel metal oxide semiconductor field effect transistor (pMOSFET) in series with a pull down n-channel MOSFET (nMOSFET). The input to the driver is the input to the first inverter. The output of the first inverter is the input to the second inverter and the output of the second inverter is the output of the driver.
Point-to-point on-chip interconnects between and within microprocessor datapath Functional Unit Blocks (FUBs) have evolved with integration as major on-chip performance and power bottlenecks. A reason for this is that interconnect capacitance per unit length, dominated by sidewall fringing and cross-coupling, may increase hyperbolically with lateral dimension scaling and hence scale slower than gate capacitance does, despite technology enhancements such as low-K dielectric materials and copper metallization.
Dynamic threshold (Vt) based circuit techniques have been investigated for low-voltage datapath circuits and interconnect drivers. See, e.g., F. Assaderaghi et al., “A Dynamic Threshold Voltage MOS (DTMOS) for Very Low Voltage Operation,” IEEE Electron Device Letters, December 1994, pp. 510-512; and U.S. Pat. No. 5,559,368. These circuits possess “dynamic” Vt transistors, i.e., transistors whose Vt changes as the gate switches. Therefore, as the input transitions, the gate-to-bulk forward bias voltage of the switching transistor increases, causing a Vt reduction (due to body effect) as the gate switches. However, since the bulk terminals are directly tied to the inputs, the fan-in gate capacitance is now substantially higher. This significantly degrades the potential performance benefits and may contribute to higher switched capacitance, and hence higher switching power consumption. Further, since each transistor must have its gate and bulk connected, a separate well is required for each device, resulting in considerable layout area penalties.
SUMMARY OF THE INVENTION
In some embodiments, the invention includes a die having a driver circuit. The driver circuit includes a driver input node and a driver output node. An nFET pull-up transistor is connected to the driver output node, and wherein the nFET pull-up transistor is at times forward body biased and the forward body bias is substantially greatest when a signal at the driver input node begins to switch high and substantially least when the switching has already essentially occurred.
In some embodiments, the driver includes a first inverter to receive an input signal from the driver input node and provide an inverted input signal at a first inverter output node. The driver includes second inverter to receive the inverted input signal from the first inverter output node and provide a driver output signal at the driver output node. The driver includes an nFET pull-up transistor connected between the driver output node and a power supply node, the nFET pull-up transistor having a gate tied to the driver input node.
In some embodiments, the nFET pull-up transistor is at times forward body biased.
Other embodiments are described and claimed.
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Aldous Alan K.
Cunningham Terry D.
Intel Corporation
Tra Quan
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