IC testing apparatus

An IC testing apparatus, which performs testing on a test device using test signals each consisting of test pulses, comprising:

• first series circuit means which consists of a skew adjusting circuit receiving a test signal and a driver, wherein the driver converts an output signal of the skew adjusting circuit in voltage to match with the test device, so that an output signal of the driver is sent to the test device;
• second series circuit means which is connected in parallel with the first series circuit means, wherein the second series circuit means consists of a comparator for comparing an input signal thereof given from the test device with a reference value and a skew adjusting circuit receiving an output signal of the comparator;
• first decision means for making a decision as to whether an output of the first series circuit means delays or advances from a first decision strobe signal which synchronizes with the test signal, thus producing a first decision signal;
• reference signal generating means for generating a reference signal which simulates the test signal;
• second decision means, coupled with the second circuit means in series, for making a decision as to whether an output of the second series circuit means delays or advances from a second decision strobe signal which synchronizes with the reference signal, thus producing a second decision signal;
• multiplexer means for changing over connections thereof in such a way that when adjusting a driver skew, an output of the first series circuit means is transmitted to the first decision means, whilst when adjusting a comparator skew, the reference signal outputted from the reference signal generating means is transmitted to the second series circuit means;
• skew counting means for counting an amount of skew corrections based on the first decision signal and/or the second decision signal with a precision which is designated in advance, thus creating skew correction data;
• and
• control means for controlling the first series circuit means and/or the second series circuit means to adjust the driver skew and/or the comparator skew on the basis of the skew correction data.