Low voltage indicator with a self-biased driver circuit

Details Low voltage indicator with a self-biased driver circuit Low voltage indicator with a self-biased driver circuit

1994-07-08

1996-11-26

Callahan, Timothy P.

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Current driver

327 80, 327482, 327483, 327484, 340660, H03K 1718, H03K 17615

Patent

active

055789501

ABSTRACT:
A low voltage indicator circuit including a self-biased driver circuit. A voltage at the output terminal is used to create a bias voltage to operate the driver when less than a threshold voltage is present on at least one voltage supply line. A transistor for supplying base drive current to the driver has a base coupled to the at least one voltage supply line in one embodiment and to the bias circuit in other embodiments. The transistor in the one embodiment provides base drive current to the driver when voltage on the at least one voltage supply line is less than the voltage on the output terminal by at least a predetermined amount. In other embodiments, the bias circuit may include a FET or resistor coupled between the output terminal and the base of a bias circuit transistor. The bias circuit transistor has a terminal connected to a bias resistor for providing current through the bias resistor when the bias circuit transistor is turned on. A switch connected to the base of the bias circuit transistor selectively directs the current from the FET or resistor to or away from the base of the bias circuit transistor. Current is directed to the base of the bias circuit transistor when less than a threshold voltage is present on the at least one voltage supply line. This causes current to flow through the bias resistor developing a bias voltage thereacross.

REFERENCES:
patent: 4056765 (1977-11-01), Scheidler et al.
patent: 4574221 (1986-03-01), Hess et al.
patent: 4574276 (1986-03-01), Sato
patent: 4616144 (1986-10-01), Hideshima et al.
patent: 4947055 (1990-08-01), Shekhawat et al.
patent: 4980578 (1990-12-01), Shaffer et al.
patent: 5047662 (1991-09-01), Edwards

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