US Patent 7940072 Timing generator and semiconductor test apparatus

A variable delay circuit has a simple configuration for being incorporated in a timing generator to control a delay time in real time and assure a timing margin. The variable delay circuit of the timing generator includes a delay circuit having a plurality of cascaded clock buffers; a plurality of cascaded data buffers; and data holding circuits for outputting data to the data buffers in accordance with the clock from the delay circuit. The delay amount added to the data by the data buffers is made identical to the delay amount added to the clock by the clock buffers.