Patent ID: 7812589

Claim:
A current source configured for substantially seamless range switching, comprising: a first resistor network having an input and an output, wherein the resistance of the first resistor network is dynamically configurable; a second resistor network having an input and an output, wherein the resistance of the second resistor network is dynamically configurable, the output of the first resistor network is connected to the input of the second resistor network, and the output of the second resistor network is configured to be connected to provide current to a device under test; a first differential amplifier having an output, a non-inverting input and an inverting input, the non-inverting input connected to the input of the first resistor network and the inverting input connected to the output of the first resistor network; a second differential amplifier having an output, a non-inverting input and an inverting input, the non-inverting input connected to the input of the second resistor network and the inverting input connected to the output of the second resistor network; a first digital potentiometer having a first input, a second input and an output, the first input connected to the output of the first differential amplifier and the second input connected to the output of the second differential amplifier, wherein the first digital potentiometer is configured to provide a signal at the output that includes, in a first selectable proportion, a combination of a signal at the first input of the first digital potentiometer and of a signal at the second input of the first digital potentiometer; an operational amplifier having a non-inverting input, an inverting input and an output, the output connected to the input of the first resistor network and the inverting input connected to the output of the first digital potentiometer; and a second digital potentiometer having a first input, a second input and an output, wherein the second digital potentiometer is configured to provide a signal at the output that includes, in a second selectable proportion, a combination of a signal at the first input of the second digital potentiometer and of a signal at the second input of the second digital potentiometer, the output of the second digital potentiometer connected to the non-inverting input of the operational amplifier.