Patent ID: 7129695

Claim:
An electrical test circuit comprising: a bridge configuration having two paths between two nodes, a buffer having an output coupled to one of the paths, wherein the buffer is adapted to either provide a defined potential or a high impedance, a capacitor connected to the output of the buffer, and a signal of a device under test—DUT—adapted to be coupled to another one of the paths, wherein one of the nodes of the bridge configuration is switchable connected to a first current source and the other one of the nodes of the bridge configuration is switchable connected to a second current source, wherein the test circuit operates in both an active-load mode and a sampling mode, and in the active-load mode, the output of the buffer provides a defined potential, the first current is provided to the device under test when the potential of the signal of the device under test is smaller than the potential at the output of the buffer, and the second current is provided to the device under test when the potential of the signal of the device under test exceeds the potential at the output of the buffer; and in the sampling mode, the output of the buffer provides a high impedance, and the course of the potential at the output of the buffer substantially follows the course of the potential of the signal of the device under test as long as the first and the second current are connected to the one node and other one node, respectively.