Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
2001-02-20
2002-06-25
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S538000, C327S542000, C327S378000, C327S256000, C323S311000, C323S315000
Reexamination Certificate
active
06411154
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to bias circuits and, more particularly, to bias circuits that provide a constant biasing voltage regardless of the operating point of the transistor being biased.
In mobile applications, electronic equipment is required to operate in a stable manner over a fairly large temperature range (e.g., −40°F. to 100° F.). Bias circuits are used to provide stable operating points for radio frequency (RF) discrete transistors (referred to herein as “external transistors”) associated with mobile and other applications.
The use of these bias circuits eliminates unacceptable fluctuations in the operating point of the external transistor. This technique allows the biased RF discrete transistor (e.g., an NPN bipolar junction transistor (BJT) or an N-channel metal oxide semiconductor (MOS) transistor) to have its emitter (or source) directly grounded and still operate with a stable collector (or drain) current.
Prior art bias circuits can provide a constant output biasing voltage with a low temperature coefficient (TC) only for a narrow range of operating points of the external transistor. If the operating point of the external transistor falls outside a narrow, design-specific range, a stable bias cannot be guaranteed. A particular design of a prior art bias circuit, therefore, cannot be applied to applications having widely differing transistor operating points.
Hence, there is a need for a bias circuit that provides a stable, accurate, and low voltage bias independent of an external transistor's specific operating point. Further needed is a bias circuit that can provide a low voltage, stable bias over a wide temperature range.
REFERENCES:
patent: 4282477 (1981-08-01), Ahmed
patent: 4352056 (1982-09-01), Cave et al.
patent: 4447784 (1984-05-01), Dobkin
patent: 4506208 (1985-03-01), Nagano
patent: 5039878 (1991-08-01), Armstrong et al.
Deckers, Et Al., “Current Stabilization Made Easy”, Components XXX (1995), No. 6, pp. 35-36.
Callahan Timothy P.
Luu An T.
Semiconductor Components Industries LLC
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