JPS56134392A - Programmable monolithic integrated circuit - Google Patents

Abstract

PURPOSE:To enable a P-N-P-N circuit to turn on normally when P-ROM increases in capacity and the number of P-N-P-N circuits also increases, by flowing a small current to bases of N-P-N transistors of the P-N-P-N circuit constituting a writing circuit. CONSTITUTION:For example, gates 1 and 3 of column selecting circuit 22 of the decoder composed of diode matrix 30 and gates 1... are held at the high level, and gates 2 and 4 at the low level, selecting the P-N-P-N circuit of transistors Q2 and Q3. So that a minute current will flow the base of N-P-N transistor Q3, a voltage high enough to turn on Zener diode D1 of applying circuit 24 is applied, and then the minute current flows from the base to the emitter of transistor Q3 and then to a memory cell. Next, flowing a write current from write terminal W turns on the P-N-P-N circuit easily because transistors Q2 and Q3 of the selected P-N-P-N circuit are activated, so that even when P-ROM increases in capacity and the number of P-N-P-N circuits also increases, the P-N-P-N circuits is turned on normally.