Current mode sample-and-hold circuit
First Claim
1. A monolithically integrated current mode sample-and-hold circuit, comprising:
- amplifier means having an output for providing a gain, wherein said amplifier means is a differential amplifier having a first input which is an inverting input, and a second input which is a non-inverting input, wherein the first input is coupled to the output;
current mirror means having a first leg coupled to the said amplifier means from which a first current to be sampled is drawn, and having a second leg for providing a second current; and
charging means operatively coupled to the output of said amplifier means operating in a closed loop for storing a bias signal, the bias signal biasing said current mirror means such that the first leg supplies the first current, and the second leg continues to supply the second current, which is representative of the first current, after operatively decoupling said charging means from said amplifier means, wherein said charging means is a parasitic capacitance of said current mirror means.
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Accused Products
Abstract
The current mode sample-and-hold circuit includes a differential amplifier having a non-inverting input coupled to a first leg of a current mirror from which a first current to be sampled is drawn. An inverting input of the differential amplifier is coupled to its output and further coupled to a capacitor through a sample hold switch. The first current drawn from the first leg of the current mirror causes the capacitor to charge, through the differential amplifier. The charged capacitor is coupled to the current mirror and biases the current mirror so as to provide the required first current. Opening the sample hold switch causes the capacitor to maintain a bias level determined by the first current. The bias signal in turn causes a mirrored current flowing in a second leg of the current mirror to be maintained, even in the absence of the first current. Thus an input current is sampled and a corresponding output current is provided. The capacitor operates in a feedback loop for improving accuracy. Furthermore, the capacitor is isolated from both the input and output providing high frequency capability. Alternatively, the sample hold switch may be replaced by a diode for providing a peak detector function.
26 Citations
22 Claims
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1. A monolithically integrated current mode sample-and-hold circuit, comprising:
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amplifier means having an output for providing a gain, wherein said amplifier means is a differential amplifier having a first input which is an inverting input, and a second input which is a non-inverting input, wherein the first input is coupled to the output; current mirror means having a first leg coupled to the said amplifier means from which a first current to be sampled is drawn, and having a second leg for providing a second current; and charging means operatively coupled to the output of said amplifier means operating in a closed loop for storing a bias signal, the bias signal biasing said current mirror means such that the first leg supplies the first current, and the second leg continues to supply the second current, which is representative of the first current, after operatively decoupling said charging means from said amplifier means, wherein said charging means is a parasitic capacitance of said current mirror means. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A monolithically integrated current mode sample-and-hold circuit, comprising:
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amplifier means having an output for providing a gain; current mirror means having a first leg coupled to the said amplifier means from which a first current to be sampled is drawn, and having a second leg for providing a second current; and charging means operatively coupled to the output of said amplifier means operating in a closed loop for storing a bias signal, the bias signal biasing said current mirror means such that the first leg supplies the first current, and the second leg continues to supply the second current, which is representative of the first current, after operatively decoupling said charging means from said amplifier means, wherein said charging means is a parasitic capacitance of said current mirror means.
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9. A monolithically integrated current mode sample-and-hold circuit, comprising:
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a differential amplifier having an inverting input coupled to an output thereof, and a non-inverting input; a current mirror having a bias terminal coupled to the output of said differential amplifier for receiving a bias signal, a first leg coupled to the non-inverting input for sinking a first current, and a second leg for providing a second current; charging means coupled between the output of said differential amplifier and a supply voltage for carrying a charging current that flows through said differential amplifier for determining the magnitude of the bias signal; and a first switch coupled to said charging means for resetting the bias signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A monolithically integrated current mode sample-and-hold circuit, comprising:
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a differential amplifier having an inverting input coupled to an output thereof, and a non-inverting input; a current mirror having a bias terminal for receiving a bias signal, a first current carrying leg coupled to the non-inverting input for sinking a first current, and a second current carrying leg for providing a second current; a first switch having a first terminal coupled to the output of said differential amplifier, and a second terminal coupled to the bias terminal; a capacitor coupled between a first supply voltage and the bias terminal for carrying a charging current that flows through the differential amplifier and defines the magnitude of the bias signal; and a second switch coupled across said capacitor for resetting the bias signal. - View Dependent Claims (19, 20, 21, 22)
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Specification