Patent ID: 7548699
Filing Date: 2009-06-16
Classification: H04B

Abstract:
1. 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.