Driver circuits for switching transistors
First Claim
1. A driver circuit for switching a transistor from a first state in which the transistor switch is closed such that an input signal is transferred to an output and a second state in which the transistor switch is open, the driver circuit comprises:
- a first reference node for receiving a first reference voltage signal;
a second reference node for receiving a second reference voltage signal;
maximum detection means coupled to receive the input signal and the first reference voltage signal and for providing at an output the greater of the two signals, the output of the maximum detection means being selectively coupled to the gate electrode of the transistor switch;
minimum detection means coupled to receive the input signal and the first reference voltage signal and for providing at an output the lesser of the two signals;
voltage shifting means having an input selectively coupled to the second reference node and to the output of the minimum detection means and an output coupled to the gate electrode of the transistor switch;
wherein in the second state the output of the maximum detection means is coupled to the gate electrode of the transistor switch and the output of the voltage shifting means and the input of the voltage shifting means is coupled to the second reference voltage signal, and wherein in the first state, the output of the minimum detection means is coupled to the input of the voltage shifting means such that the output of the voltage shifting means is shifted by the minimum output signal to a voltage level which corresponds to the difference between the second reference voltage signal and the minimum output signal such that the voltage on the gate electrode of the transistor switch is dependent on the maximum output signal and the signal at the output of the voltage shifting means, whereby the gate-to-source voltage of the transistor switch is independent of the input signal.
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Accused Products
Abstract
A driver circuit (8) is arranged to switch a transistor (10) of a switched capacitor circuit, or transistors (62 and 64) of a differential switched capacitor circuit, between a first state, in which the transistor switch is closed whereby an input signal (VINP) is transferred to an output, and a second state, in which the transistor switch is open. The driver circuit includes a maximum and a minimum selection (12, 14) between the input signal and a reference voltage (VAG) , a voltage shift element (26), and switches (16, 18, 20, 22, 24), coupled to receive the input signal (VINP) and to the gate electrode of the transistor switch (10), which ensures that the gate-to-source voltage of the transistor switch (10), in the first and second states, is independent of the input signal (VINP).
17 Citations
21 Claims
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1. A driver circuit for switching a transistor from a first state in which the transistor switch is closed such that an input signal is transferred to an output and a second state in which the transistor switch is open, the driver circuit comprises:
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a first reference node for receiving a first reference voltage signal; a second reference node for receiving a second reference voltage signal; maximum detection means coupled to receive the input signal and the first reference voltage signal and for providing at an output the greater of the two signals, the output of the maximum detection means being selectively coupled to the gate electrode of the transistor switch; minimum detection means coupled to receive the input signal and the first reference voltage signal and for providing at an output the lesser of the two signals; voltage shifting means having an input selectively coupled to the second reference node and to the output of the minimum detection means and an output coupled to the gate electrode of the transistor switch; wherein in the second state the output of the maximum detection means is coupled to the gate electrode of the transistor switch and the output of the voltage shifting means and the input of the voltage shifting means is coupled to the second reference voltage signal, and wherein in the first state, the output of the minimum detection means is coupled to the input of the voltage shifting means such that the output of the voltage shifting means is shifted by the minimum output signal to a voltage level which corresponds to the difference between the second reference voltage signal and the minimum output signal such that the voltage on the gate electrode of the transistor switch is dependent on the maximum output signal and the signal at the output of the voltage shifting means, whereby the gate-to-source voltage of the transistor switch is independent of the input signal. - View Dependent Claims (2, 3, 4, 5, 6, 8)
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7. A driver circuit according to claim I wherein the maximum detection means has a first input for receiving the input signal and a second input for receiving the first reference voltage signal and comprises:
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a first transistor having a first current electrode, a second current electrode coupled to a third reference voltage node and a gate electrode coupled to the first input; a second transistor having a first current electrode coupled to the output of the maximum detection means, a second current electrode coupled to the first current electrode of the first transistor and a gate electrode coupled to the second input; a current supply means coupled to the first current electrode of the second transistor for supplying current thereto such that the first and second transistors operate in the sub-threshold region whereby the greater of the voltage signals at the first and second inputs is outputted to the output of the maximum detection means.
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9. A driver circuit for a differential switched capacitor circuit, the driver circuit being arranged to switch a pair of differential transistor switches from a first state in which the switches are closed such that respective first and second input signals, which form therebetween a differential input signal, are transferred to first and second outputs thereof and a second state in which the switches are open, the driver circuit comprising:
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a first reference node for receiving a first reference voltage signal, the first reference voltage signal having a level substantially equal to half the sum of the first and second input signals; a second reference node for receiving a second reference voltage signal; first maximum detection means coupled to receive the first input signal and the first reference voltage signal and for providing at an output the greater of the two signals, the output of the first maximum detection means being selectively coupled to the gate electrode of a first transistor switch of the pair of transistor switches; second maximum detection means coupled to receive the second input signal and the first reference voltage signal and for providing at an output the greater of the two signals, the output of the second maximum detection means being selectively coupled to the gate electrode of a second transistor switch of the pair; first voltage shifting means having an input selectively coupled between the second reference node and the output of the second maximum detection means and an output coupled to the gate electrode of the first transistor switch; second voltage shifting means having an input selectively coupled between the second reference node and the output of the first maximum detection means and an output coupled to the gate electrode of the second transistor switch; wherein in the second state the output of the first maximum detection means is coupled to the gate electrode of the first transistor switch, the output of the first voltage shifting means and the input of the second voltage shifting means and the output of the second maximum detection means is coupled to the gate electrode of the second transistor switch, the output of the second voltage shifting means and the input of the first voltage shifting means, and wherein in the first state, the inputs of the first and second voltage shifting means are coupled to the second reference node such that the outputs of the first and second voltage shifting means are each shifted by the second reference voltage signal to voltage levels which correspond to the difference between the second maximum output signal and the second reference voltage signal, and the first maximum output signal and the second reference voltage signal, respectively, such that the voltages on the gate electrodes of the first and second transistor switches are dependent on the first maximum output signal and the output of the first voltage shifting means, and second maximum output signal and the output of the second voltage shifting means, respectively, whereby the gate-to-source voltages of the first and second transistor switches are independent of the differential input signal. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A driver circuit for a differential switched capacitor circuit, the driver circuit being arranged to switch a pair of differential transistor switches from a first state in which the switches are closed such that respective first and second input signals, which form therebetween a differential input signal, are transferred to first and second outputs thereof and a second state in which the switches are open, the driver circuit comprising:
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a first reference node for receiving a first reference voltage signal, the first reference voltage signal having a level substantially equal to half the sum of the first and second input signals; a second reference node for receiving a second reference voltage signal; first minimum detection means coupled to receive the first input signal and the first reference voltage signal and for providing at an output the lesser of the two signals, the output of the first minimum detection means being selectively coupled to the gate electrode of a first transistor switch of the pair of transistor switches; second minimum detection means coupled to receive the second input signal and the first reference voltage signal and for providing at an output the lesser of the two signals, the output of the second minimum detection means being selectively coupled to the gate electrode of a second transistor switch of the pair; first voltage shifting means having an input selectively coupled between the second reference node and the output of the second minimum detection means and an output coupled to the gate electrode of the first transistor switch; second voltage shifting means having an input selectively coupled between the second reference node and the output of the first minimum detection means and an output coupled to the gate electrode of the second transistor switch; wherein in the second state the output of the first minimum detection means is coupled to the gate electrode of the first transistor switch, the output of the first voltage shifting means and the input of the second voltage shifting means and the output of the second minimum detection means is coupled to the gate electrode of the second transistor switch, the output of the second voltage shifting means and the input of the first voltage shifting means, and wherein in the first state, the inputs of the first and second voltage shifting means are coupled to the second reference node such that the outputs of the first and second voltage shifting means are each shifted by the second reference voltage signal to voltage levels which correspond to the difference between the second minimum output signal and the second reference voltage signal, and the first minimum output signal and the second reference voltage signal, respectively, such that the voltages on the gate electrodes of the first and second transistor switches are dependent on the first minimum output signal and the output of the first voltage shifting means, and second minimum output signal and the output of the second voltage shifting means, respectively, whereby the gate-to-source voltages of the first and second transistor switches are independent of the differential input signal. - View Dependent Claims (17, 18, 19, 20, 21)
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Specification