Patent ID: 7772892
Filing Date: 2010-08-10
Classification: G01R

Abstract:
1. A differential hybrid circuit that receives reception differential signals outputted from a device to be tested via differential lines, and compares a differential amplitude of the reception differential signals with a predetermined threshold voltage, as well as supplying transmission differential signals to the device to be tested via the differential lines, the differential hybrid circuit comprising: a first I/O terminal to which one of the reception differential signals and one of the transmission differential signals are inputted/outputted; a second I/O terminal to which the other of the reception differential signals and the other of the transmission differential signals are inputted/outputted; a main driver amplifier that generates first differential signals based on pattern data to be transmitted to the device to be tested; a first resistance provided between one of output terminals of the main driver amplifier and the first I/O terminal; a second resistance provided between the other output terminal of the main driver amplifier and the second I/O terminal; a replica driver amplifier that generates second differential signals based on the pattern data; a third resistance first terminal of which is connected to one of output terminals of the replica driver amplifier; a fourth resistance first terminal of which is connected to the other output terminal of the replica driver amplifier; a first subtractor that generates a first electric potential difference signal corresponding to an electric potential difference between an electric potential at the first I/O terminal and an electric potential at the second terminal of the third resistance; a second subtractor that generates a second electric potential difference signal corresponding to an electric potential difference between an electric potential at the second I/O terminal and an electric potential at the second terminal of the fourth resistance; a first sample hold circuit that samples the first electric potential difference signal at a designated timing, and holds it thereafter; a second sample hold circuit that samples the second electric potential difference signal at a designated timing, and holds it thereafter; a comparison unit that compares a signal corresponding to a difference between respective output signals from the first and the second sample hold circuits, with a predetermined threshold value; and a latch circuit that latches an output from the comparison unit, wherein the sampling timings of the first and the second sample hold circuits and a latch timing of the latch circuit, can be adjusted independently.