Early voltage and beta compensation circuit for a current mirror
First Claim
1. An Early voltage and beta compensated cascode current mirror comprising:
- a cascode current mirror having an input stage responsive to an input current, a current mirror circuit having a first stage responsive to the input stage and a second stage responsive to the first stage, and an output stage responsive to the second stage for providing an output voltage and current; and
a compensation circuit, responsive to the cascode current mirror, having a first compensation stage, a second compensation stage and a bootstrapping buffer, the first compensation stage, in response to a change in the output voltage, impressing an equal change in voltage on the second compensation stage, the second compensation stage thereby providing a change in current to the cascode current mirror for cancelling current errors induced by base modulation effects in the output stage, the bootstrapping buffer, in response to the change in voltage, impressing an equal change in voltage on the first compensation stage to prevent errors from base current modulation in the first compensation stage, the first and second compensation stages further providing base currents to the cascode current mirror for cancelling base current errors in the output current induced by the cascode current mirror.
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Accused Products
Abstract
An Early voltage and beta current compensated cascode current mirror includes a cascode current mirror having an input stage responsive to an input current, a current mirror circuit having a first stage responsive to the input stage and a second stage responsive to the first stage, and an output stage responsive to the second stage for providing an output voltage and current; and a compensation circuit, responsive to the cascode current mirror, having a first compensation stage, a second compensation stage and a bootstrapping buffer, the first compensation stage, in response to a change in the output voltage, impressing a corresponding change in voltage on the second compensation stage, the second compensation stage thereby providing a change in current to the cascode current mirror for cancelling current errors induced by base current modulation in the output stage, the bootstrapping buffer, in response to the change in voltage, impressing a corresponding change in voltage on the first compensation stage to prevent errors from base current modulation effects in the first compensation stage, the first and second compensation stages further providing a base current to the cascode current mirror for cancelling base current errors in the output current induced by the cascode current mirror.
21 Citations
15 Claims
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1. An Early voltage and beta compensated cascode current mirror comprising:
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a cascode current mirror having an input stage responsive to an input current, a current mirror circuit having a first stage responsive to the input stage and a second stage responsive to the first stage, and an output stage responsive to the second stage for providing an output voltage and current; and
a compensation circuit, responsive to the cascode current mirror, having a first compensation stage, a second compensation stage and a bootstrapping buffer, the first compensation stage, in response to a change in the output voltage, impressing an equal change in voltage on the second compensation stage, the second compensation stage thereby providing a change in current to the cascode current mirror for cancelling current errors induced by base modulation effects in the output stage, the bootstrapping buffer, in response to the change in voltage, impressing an equal change in voltage on the first compensation stage to prevent errors from base current modulation in the first compensation stage, the first and second compensation stages further providing base currents to the cascode current mirror for cancelling base current errors in the output current induced by the cascode current mirror. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A beta and Early voltage compensation circuit for a current mirror having an output stage for providing an output voltage and current gain Y comprising:
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a first compensation stage, responsive to a change in the output voltage;
a second compensation stage, responsive to the first compensation stage, for providing a current to the output stage; and
a bootstrapping buffer stage, responsive to the change in output voltage, the bootstrapping buffer, in response the change in voltage, impressing an equal change in voltage on the first compensation stage to prevent errors from base current modulation effects in the first compensation stage, the first compensation stage, in response to the change in the output voltage, impressing a corresponding change in voltage on the second compensation stage, the second compensation stage thereby providing a change in current to the current mirror for cancelling current errors induced by base current modulation errors in the output stage, the first and second compensation stages further providing a base current to the cascode current mirror for cancelling base current errors introduced in the output current by the cascode current mirror. - View Dependent Claims (12, 13, 14, 15)
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Specification