System and methods to improve the performance of semiconductor based sampling system
AssigneeLinear Technology Corporation
InventorDavid M. Thomas
Life of this patent
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Abstract
Circuits and methods that improve the performance of electronic sampling systems are provided. Impedances associated with sampling semiconductor switches are maintained substantially constant during sample states, at least in part, by compensating for encountered input signal variations in order to reduce or minimize signal distortion associated with sampled signals that pass through the sampling switch.
Claims24
A sampling circuit that operates in at least a sample state and a hold state comprising:
- a semiconductor switch that operates in at least a non-conductive mode and a conductive mode as directed by an amount of charge applied to a control terminal, the semiconductor switch being coupled between a source of an input signal and an output terminal;
- an initialization circuit that is operative to selectively couple an initialization signal at least partially representative of the input signal to the control terminal, during an initialization state;
- a charge generator for producing a charge that is distinct from the input signal and coupled to the control terminal to control the switch;
- and
- a control circuit that is operative to selectively direct the charge generator to deliver a predetermined amount of charge to the control terminal such that the impedance of the semiconductor switch during a sample state is maintained substantially constant.
A method of transitioning a semiconductor switch from a high impedance, substantially non-conductive state to a low impedance, substantially conductive state, the semiconductor switch being coupled between a source of an input signal and an output terminal, the method comprising:
- determining a capacitance associated with the semiconductor switch control terminal when the semiconductor switch, in its conductive state, reaches a desired impedance value;
- determining an amount of charge absorbed by the semiconductor switch control terminal capacitance when the semiconductor switch, in its conductive state, reaches a desired impedance value;
- and
- providing a charge to a control terminal of the semiconductor switch which is substantially equal to or greater than the amount of charge absorbed by the gate to channel capacitance, such that the semiconductor switch turns ON, and an impedance of the semiconductor switch is maintained substantially constant.
Dependencies are inferred from the claim text.