| 摘要 |
<p>PURPOSE:To detect the micro change of a current at high speed by generating the change of a voltage with a resistance element inserted between first and second transistors, and detecting it with a differential amplifier comprised of third and fourth transistors. CONSTITUTION:When a row selection signal X2 goes to an H level, the N- channel MOSFET 12 of a ROM cell is turned on, and the current flows from a power source 1 via an NPN type bipolar transistor (Tr) 3, a resistor 14, a Tr 4, and a MOSFET 8. Therefore, voltage drop occurs at both ends of the resistor 14, and the potential of a connecting point 13 drops. The output terminal 19 of a differential amplifier circuit comprised of Trs 5, 6 and a power source MOSFET 7 goes to a low level when the voltage of the connecting part 13 is less than preset potential D to be applied on the base of the Tr 6, and when the signal X2 goes to the low level and the potential of the connecting point 13 rises and exceeds the preset potential D, the potential E of the output terminal 19 starts to go to the H level. Since the change of the potential of the connecting point 13 is low, delay time is remarkably shortened, which enables the readout of a ROM to be performed at high speed.</p> |
