Method of and apparatus for biasing switches
First Claim
1. A switch responsive to a switch control signal, the switch comprising one or more stages, at least a first one of the stages comprises:
- a first signal terminal;
a second signal terminal;
an electrically controllable impedance connected between the first and second signal terminals, the electrically controllable impedance arranged to vary its impedance in response to a stage control signal; and
a stage control circuit having a first control circuit input configured to receive a switch control signal;
where the stage control circuit has a second control circuit input responsive to a signal voltage at either the first signal terminal or the second signal terminal, a low pass filter is provided in a path of the signal voltage, and the stage control circuit is adapted to generate the stage control signal as function of voltage at the first and second control circuit inputs.
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Accused Products
Abstract
A control circuit is provided for controlling the voltage at the gate terminal of a field effect transistor acting as a switch. The voltage, at for example, the source terminal of the transistor can be provided to a low pass filter and is then voltage translated to provide the gate signal. The filtering can be arranged so as to compensate for the effect of parasitic capacitances within the transistor, thereby linearizing its frequency response. The voltage translation can help to limit voltage differences between the gate and channel of the transistor. This can be significant as relatively fast transistors, as might be used in microwave circuits, may fail with relatively modest voltages at their gates.
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Citations
20 Claims
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1. A switch responsive to a switch control signal, the switch comprising one or more stages, at least a first one of the stages comprises:
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a first signal terminal; a second signal terminal; an electrically controllable impedance connected between the first and second signal terminals, the electrically controllable impedance arranged to vary its impedance in response to a stage control signal; and a stage control circuit having a first control circuit input configured to receive a switch control signal; where the stage control circuit has a second control circuit input responsive to a signal voltage at either the first signal terminal or the second signal terminal, a low pass filter is provided in a path of the signal voltage, and the stage control circuit is adapted to generate the stage control signal as function of voltage at the first and second control circuit inputs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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- 14. A control circuit for a switch, the control circuit comprising a low pass filter configured to receive a signal from a first side of the switch to form a low pass filtered version of a voltage at the first side of the switch, and a signal generation circuit configured to generate a variable signal to be provided to at least one field effect transistor forming the switch, where the variable signal varies in response to an output of the low pass filter.
- 19. A method of controlling a switch, where the switch is formed from a plurality of series connected stages, each stage of the series connected stages comprising a respective transistor connected between first and second terminals, the method comprising modifying the frequency content of a control signal provided to the transistor in order to compensate for parasitic components associated with the transistor.
Specification