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US 7,548,699 B2Granted
Channel-length modulation (CLM) compensation method and apparatus
AssigneeAvago Technologies ECBU IP (Singapore) Pte. Ltd.
InventorsKah Weng Lee, Bin Zhang
Life of this patent
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Abstract
A power supply generates a supply voltage that varies from a first voltage level to a second voltage level. A first current source is coupled to the power supply and generates a current that varies due to channel-length modulation. A channel-length modulation (CLM) compensation mechanism is provided to reduce the current variation of the first current source by compensating the channel-length modulation (CLM) of the first current source.
Claims15
An optocoupler system, comprising:
- a light source that when driven by a drive signal is configured to generate light;
- a first current source coupled to the light source and coupled to a voltage that varies, the drive signal varying in response to the changing voltage due to channel length modulation;
- a channel length modulation compensation mechanism coupled to the first current source and configured to reduce the variation in the drive signal of the first current source caused by the channel length modulation of the current source, the channel length modulation mechanism comprising first and second current mirrors, a voltage source, and a resistor, the resistor having a value based on the expression:
- 1/(delta Y/delta X), wherein delta Y is the difference between a second drain current of the second current mirror and a first drain current of the first current mirror, and delta X is the difference between a second drain to source voltage of the second current mirror and a first drain to source voltage of the first current mirror.
1 more element
A system, comprising:
- a power supply configured to generate a supply voltage that varies from a first voltage level to a second voltage level;
- a first current source operably coupled to the power supply and configured to generate a current that varies due to channel-length modulation;
- and
- a channel-length modulation (CLM) compensation mechanism, operably coupled to the first current source, and configured to reduce the current variation of the first current source by compensating the channel-length modulation (CLM) of the first current source, the channel length modulation mechanism comprising first and second current mirrors, a voltage source, and a resistor, the resistor having a value based on the expression:
- 1/(delta Y/delta X), wherein delta Y is the difference between a second drain current of the second current mirror and a first drain current of the first current mirror, and delta X is the difference between a second drain to source voltage of the second current mirror and a first drain to source voltage to the first current mirror.
2 more elements
Dependencies are inferred from the claim text.