| 摘要 |
PURPOSE:To set the internal state of an IC easily by the occupancy of a small area by mounting a reverse-biased P-N junction diode into an IC chip through a high-impedance element and connecting a switching element in parallel with the high-impedance element. CONSTITUTION:When testing an IC chip, an MOS transistor Tr3 is kept under an OFF state, an a P-N junction diode 1 is irradiated by convergent laser beams. Consequently, photocurrents flow through the diode 1, and cathode potential drops. As a result, an H level output acquired in a C-MOS inverter 4 is trigger- signaled, and the internal state of an IC element required is set. The Tr3 is set under an ON state and both ends of a pull-up resistor 2 are short-circuited previously on normal operation except the time of a test. When the Tr3 is not fitted, an input to the inverter 4 shaping a waveform is pulled up by a comparatively high resistance value, and impedance is increased, thus resulting in the state of the easy reception of the effect of noises. When the Tr3 is mounted and turned ON previously on normal operation, an output from the inverter 4 is kept stably at an L level.
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