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US 2010/0244907 A1Published application
Low speed, load independent, slew rate controlled output buffer with no dc power consumption
AssigneeFairchild Semiconductor Corporation
InventorsNickole A. Gagne, James B. Boomer, Roy L. Yarbrough
Life of this patent
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Abstract
An output buffer utilizes capacitive feedback to control the output slew rate largely independent of load capacitance. The invention slows the rising and falling slew rates and via a capacitance feedback reduces the effect of load capacitance on slew rate, and uses no DC current. Transistor switches are employed to isolate and reduce noise and interaction among the circuit components and functions.
Claims9
An output buffer comprising:
- an inverter with an input connected to an input signal, the inverter defining an inverter output;
- a pull up output transistor with its drain connected to a signal output;
- a resistor with one end connected to the inverter output and the other end connected to the gate of the pull up transistor;
- a feedback capacitor connected between the gate of the pull up transistor and the signal output;
- wherein when the input signal goes high, the inverter output goes low and the gate voltage starts to go low turning on the pull up output transistor, the signal output starts to go high, wherein the signal output going high drives current through the feedback capacitor thereby slowing the fall of the gate voltage and slows the rises of the signal output, and wherein the output buffer uses no DC current.
2 more elements
A method for controlling the edge rise and fall times of an output, the method comprising the steps of:
- inverting an input signal and producing an inverter output;
- driving the gate from the inverter output and turning on a pull up transistor via a resistor
- driving the output from the drain of the pull up output transistor;
- feeding back the output via a capacitor connected to the gate of the pull up transistor;
- wherein when the feedback operates to counter the inverter output, and wherein no DC current is used.
2 more elements
Dependencies are inferred from the claim text.