Active semiconductor device with matched reference component mai

Details Active semiconductor device with matched reference component mai Active semiconductor device with matched reference component mai

1996-05-09

1997-11-04

Sterrett, Jeffrey L.

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

323280, G05F 1575

Patent

active

056843909

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to an optimization circuit for use with an active semi-conductor device, such as a MOS or CMOS field effect transistor circuit.


DESCRIPTION OF THE PRIOR ART

A wide range of gate lengths is observed in advanced CMOS and GaAs devices due to process variations over long periods of time. This gives rise to a wide range in electrical parameters, particularly speed and breakdown voltage. Analagous problems occur in bipolar devices, where base width is difficult to control.
As a result of the spread of breakdown voltages from one device to the next, it is customary to design circuitry to operate well away from the breakdown voltage so that the circuit specifications do not result in a significant wastage of components and reduction in product yield. The unfortunate consequence of this requirement is that the operating frequency of the circuit is reduced. The reduction in operating frequency is compounded by the Early effect, which causes the frequency response to decrease as the supply voltage is moved further away from the breakdown voltage.
Previously, guard banding has been employed to distance the circuit operating conditions from the minimum breakdown voltage but inevitably speed performance is adversely affected. There is a trade-off between performance and reject rate. The smaller the guard band, the better the performance but the higher the reject rate. In the production of any semi-conductor device, the objective is to obtain the lowest reject rate, or highest yield, possible.
GB 2 146 145 describes an internal high voltage regulator for integrated circuits, which includes matched components that are designed to breakdown first in the event of an excessive internal programming voltage, thereby protecting the operating circuitry. This patent does not disclose how to optimize the performance of a circuit.
The object of the invention is to alleviate the aforementioned problems.


SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a method of improving the performance of an active semiconductor device with a voltage-controllable channel length, comprising providing a matched reference component having similar operating characteristics to said active semiconductor device, characterized in that a current is supplied to said matched reference component to cause the breakdown thereof, the breakdown voltage of said matched reference component is continually monitored, and the operating voltage of said active semiconductor device is continually maintained to lie just below the voltage at which breakdown occurs.
The invention can be applied to any electrical circuit which has well matched active components. In the case of discrete components, the operating voltage can be set by a linear voltage control circuit comprising an amplifier and a power transistor forming a pass element. The function of the pass element is to reduce the voltage to a value of V.sub.o below the reference device breakdown voltage. In the case of a bipolar circuit, the same technique can be used or an operational amplifier can be used to buffer the reference voltage, with the required voltage drop being obtained from a level shifting circuit.
The reference device is preferably maintained in close physical proximity on the same circuit to the active device. As a result, the reference component is influenced by the same external factors as the active component and consequently its breakdown voltage varies in a similar fashion.
In one embodiment, a small current is forced through the reference component with a current limiting device to cause it to breakdown, and the breakdown voltage is then presented to an input of an operational amplifier, which at its output provides a control voltage.
In a further aspect, the invention provides an optimization circuit comprising an active semiconductor device having a channel with an identifiable breakdown voltage, a voltage regulator for applying a desired output voltage to said device, said output voltage determining the l

REFERENCES:
patent: 3970875 (1976-07-01), Leehan
patent: 4158804 (1979-06-01), Butler et al.
patent: 4260946 (1981-04-01), Wheatley, Jr.
patent: 4581672 (1986-04-01), Lucero
patent: 4716307 (1987-12-01), Aoyama
patent: 4731574 (1988-03-01), Melbert
patent: 5355078 (1994-10-01), Demizu
patent: 5548205 (1996-08-01), Monticelli

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