Patent ID: 6977540
Filing Date: 2005-12-20
Classification: H03K

Abstract:
1. An isolated port apparatus comprising: an input circuit that generates an input signal in response to a data signal, the input circuit coupled to a first power and ground circuit; an output circuit that, in response to a control signal, generates an output signal that substantially replicates the data signal, the output circuit coupled to a second power and ground circuit that is isolated from the first power and ground circuit; and an optical isolator circuit that electrically isolates the input circuit from the output circuit, the optical isolator circuit generating the control signal in response to the input signal; wherein the output circuit comprises a plurality of circuit elements coupled to an output transistor, the plurality of circuit elements conditioning the control signal for input to a base input of the output transistor; wherein the plurality of circuit elements provide a voltage divider that generates a reference voltage for the control signal that is appropriate for the output transistor; and a diode, coupled between the voltage divider and a base of a first transistor of the optical isolator, that generates a maximum reference voltage level for the control signal in response to the reference voltage.