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US 8,542,055 B2Granted
Multi-level control for pass transistor gate voltage
AssigneeFairchild Semiconductor Corporation
InventorKenneth P. Snowdon
Life of this patent
Estimating the term…
Abstract
A circuit for selectively providing a signal from a source to a sink is provided. The circuit includes a field effect transistor having a conducting state and a non-conducting state, the field effect transistor having a gate, a source, and a drain. The circuit also includes a first comparator configured to provide a first output based on a difference between a source voltage at the source of the field effect transistor and a first reference voltage. Finally, the circuit includes a switching amplifier configured to apply a first gate voltage to the gate of the field effect transistor as a function of the first output of the first comparator.
Claims16
A circuit comprising:
- a field effect transistor having a conducting state and a non-conducting state, the field effect transistor having a gate, a source, and a drain;
- a first comparator configured to provide a first output based on a difference between a source voltage at the source of the field effect transistor and a first reference voltage, wherein the first output includes a first signal when the source voltage is higher than the first reference voltage and a second signal when the source voltage is lower than the first reference voltage;
- a switching amplifier configured to apply a first gate voltage to the gate of the field effect transistor in response to the first comparator providing the first signal and a second gate voltage to the gate of the field effect transistor in response to the first comparator providing the second signal, wherein both the first and second gate voltages are configured to place the field effect transistor in a conducting state;
- wherein the switching amplifier comprises:
- a first charge pump stage configured to provide the second gate voltage;
- a second charge pump stage configured to provide the first gate voltage;
- a switch configured to couple the second gate voltage to the second charge pump stage when the first comparator outputs the first signal;
- and
- wherein the second charge pump is configured to convert the second gate voltage into the first gate voltage when the first comparator outputs the first signal;
- and
- wherein the first gate voltage is higher than the second gate voltage.
8 more elements
A method for providing a signal from a source to a sink with a field effect transistor having a gate, a source, and a drain, the method comprising:
- comparing a source voltage at a source of the field effect transistor with a first reference voltage;
- applying a first gate voltage to the gate of the field effect transistor when the source voltage is higher than the first reference voltage and a second gate voltage to the gate of the field effect transistor when the source voltage is lower than the first reference voltage;
- converting an input voltage at a first charge pump to a first gate voltage to apply to the gate of the field effect transistor when the source voltage is higher than the first reference signal, wherein the first gate voltage is higher than the second gate voltage;
- wherein applying includes converting the input voltage at the first charge pump to the second gate voltage;
- and
- wherein both the first and second gate voltages are configured to place the field effect transistor in a conducting state.
3 more elements
A circuit comprising:
- a first field effect transistor having a first gate, a first source, and a first drain, the first field effect transistor configured to provide a first signal from the source to the sink;
- a second field effect transistor having a second gate, a second source, and a second drain, the second field effect transistor configured to provide a second signal from the source to the sink;
- a first comparator configured to provide a first output based on a difference between a source voltage at the first source of the first field effect transistor and a first reference voltage;
- a second comparator configured to provide a second output based on a different between a source voltage at the second source of the second field effect transistor and the first reference voltage;
- logic elements configured to receive the first output and the second output and provide a third output;
- and
- a switching amplifier configured to apply a first gate voltage to the first gate and the second gate or a second gate voltage to the first gate and the second gate as a function of the third output, wherein the switching amplifier includes:
- a first charge pump stage configured to provide the second gate voltage;
- and
- a second charge pump configured to provide the first gate voltage;
- and
- a switch configured to couple the second gate voltage to the first gate and the second gate when the third output indicates that either of the source voltage at the first source or the source voltage at the second source is lower than the first reference voltage.
9 more elements
Dependencies are inferred from the claim text.