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US 3,937,987 AGranted
Threshold detector
AssigneeRCA Corporation
InventorAdel Abdel Aziz Ahmed
Life of this patent
Estimating the term…
Abstract
Two transistors, the emitter of the first joined to the collector of the second via a resistor and two bases joined by an element such as a diode. When the input signal applied to the base electrode of the first transistor is less than a given value, neither transistor conducts; when it exceeds a second value close to this given value, substantially constant voltages develop across the diode and resistor, respectively, and the two transistors conduct a constant current.
Claims9
A threshold switch comprising:
- input, output and common terminals;
- first and second transistors, each having a base and an emitter and a collector electrode, said first transistor collector electrode being connected to said output terminal and said second transistor emitter electrode being connected to said common terminal;
- a first resistive element connected between said first transistor emitter electrode and said second transistor collector electrode;
- a second resistive element connected between said input terminal and said first transistor base electrode;
- means with first and second terminals for providing a substantially fixed offset potential responsive to current flow having a range of values between its first and second terminals;
- negligible direct current impedance means connecting said first terminal to said base electrode of said first transistor;
- and
- negligible direct current impedance means connecting said second terminal to the base electrode of said second transistor.
5 more elements
In combination:
- first and second transistors, each having base, emitter and collector electrodes, the first transistor connected at its collector electrode to an output terminal and the second connected at its emitter electrode to a point of reference potential;
- resistive means connected between the collector electrode of said second transistor and the emitter electrode of said first transistor;
- and
- means connected to the base electrode of said first transistor and responsive to a signal having a range of values applied thereto of greater than a given value for establishing a relatively constant difference in potential between said first and second base electrodes and a sufficient flow of base current into said second transistor for driving the same into saturation.
1 more element
Dependencies are inferred from the claim text.