| 摘要 |
<p>PURPOSE:To select the defective writing which does not apear without executing the writing in actual in the unwritten condition and to improve the writing yield of a programmable element by consisting so that the defective program will be selected by measuring the minumum holding current of the circuit which is consisted of a PNPN thyrister. CONSTITUTION:A PNPN driver 1 is a PNPN thyrister structure which is composed of the Darlington connection of a PNP transistor Q1 and PNP transistors Q2 and Q3. At this time, the minimum current which is held by the PNPN driver is indicated by an equation (an IRI is a current value which flows through a resistance R1). It is known that the larger current gains hQ1-hQ3 of the transistors Q1-Q3 are, the smaller a current I0 is. The current gain of the parasitic PNP transistor of a cell array inside the chip, and the current gain of the NPN transistor can be presumed by measuring the current I0. In the characteristic drawing which indicates the impedance viewed from the PNPN driver 1 when the writing cell is selected, point A becomes the minimum holding current. Thus, this point is measured.</p> |
