US Patent 7319232 Apparatus and method for high-bandwidth opto-coupler interface

An opto-coupler interface is provided. The opto-coupler interface includes a current mirror and a resistor. The opto-coupler interface is arranged such that a relatively fixed voltage is provided across the photodetector. At one end of the photodetector, the voltage is relatively fixed because the photodetector is coupled to the input of a current mirror. Because the voltage across the opto-coupler is relative fixed, the opto-coupler interface is a current interface rather than a voltage interface. Current from the photodetector is mirrored by the current mirror to provide an output mirror current. The output mirror current is provided to a resistor such that the resistor provides a voltage that is based on the output mirror current.