High-speed, bootstrap driver circuit
First Claim
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1. A circuit for driving digital signals from a signal source through an output terminal onto a line, said circuit comprising:
- an output transistor having an emitter terminal connected to said output terminal, a base terminal connected to a first current source, and a collector terminal coupled to a first voltage supply source;
a second transistor having an emitter terminal connected to said base terminal of said output transistor, a base terminal connected to a second current source, and a collector terminal coupled to said first voltage supply source;
switching means connected to said output terminal, said base terminal of said output transistor and said base terminal of said second transistor, said switching mean coupling and uncoupling said output terminal, and said base terminals of said output and second transistors to ground, responsive to a data signal from said signal source; and
capacitive means connected to said base terminal of said output transistor and to said base terminal of said second transistor through a first impedance means, said capacitive means raising the voltage to said base terminal of said second transistor to decrease the switch-on times of said output and second transistors.
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Abstract
A line driver circuit capable of operating at high speeds. The output transistor, an emitter connected to an output terminal, has a special feedback capacitor connected to its base. The feedback capacitor helps pull the output terminal high to increase the switching speed of the line driver circuit. Special current injection and removal techniques are used to speed the switching times of the PNP current supply transistors. The line driver circuit also has special circuitry to limit the output current from exceeding certain limits and for keeping the line driver circuit from overheating.
14 Citations
16 Claims
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1. A circuit for driving digital signals from a signal source through an output terminal onto a line, said circuit comprising:
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an output transistor having an emitter terminal connected to said output terminal, a base terminal connected to a first current source, and a collector terminal coupled to a first voltage supply source; a second transistor having an emitter terminal connected to said base terminal of said output transistor, a base terminal connected to a second current source, and a collector terminal coupled to said first voltage supply source; switching means connected to said output terminal, said base terminal of said output transistor and said base terminal of said second transistor, said switching mean coupling and uncoupling said output terminal, and said base terminals of said output and second transistors to ground, responsive to a data signal from said signal source; and capacitive means connected to said base terminal of said output transistor and to said base terminal of said second transistor through a first impedance means, said capacitive means raising the voltage to said base terminal of said second transistor to decrease the switch-on times of said output and second transistors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A digital logic circuit comprising:
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a first transistor having an emitter terminal connected to an output terminal, a base terminal connected to a first current source, and a collector terminal coupled to a first voltage supply source; a second transistor having an emitter terminal connected to said base terminal of said first switching transistor, a base terminal connected to a second current source, and a collector terminal coupled to said first voltage supply source; switching means connected to said output terminal, said base terminal of said first transistor and said base terminal of said second transistor, said switching means coupling and uncoupling said emitter and base terminals of said first transistor and said base terminal of said second transistor to a second voltage supply reference responsive to a digital logic signal from a signal source; and capacitive means connected to said base terminal of said output transistor and to said base terminal of said second transistor through a first impedance means, said capacitive means raising the voltage to said base terminals of said first and second transistors as said first transistor turns on to decrease the switch-on times of said first and second transistors. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification