Read amplifier for semiconductor memory cells with means to compensate threshold voltage differences in read amplifier transistors

摘要

PCT No. PCT/DE97/01027 Sec. 371 Date Nov. 12, 1998 Sec. 102(e) Date Nov. 12, 1998 PCT Filed May 21, 1997 PCT Pub. No. WO97/47010 PCT Pub. Date Dec. 11, 1997In the read amplifier a mismatch of the inception voltages of cross-coupled transistors (M5, M6) of the read amplifier are compensated by four further transistors (M1 . . . M4), whereby a defined equalizing of the bitlines advantageously takes place with these further transistors simultaneously in what is called the equalize phase. The compensation takes place in that the bitline that is connected with the transistor with the lower inception voltage is charged to a higher level in the pre-load phase. This higher bitline level is switched to the gate of the transistor connected with the other bitline. In the evaluation phase the transistor with the higher inception voltage becomes more strongly conductive. Read amplifiers of this sort are most significant for memory generations beginning at 1 Gbit, since the mismatch due to the variation of the input voltages of the transistors can no longer usefully be solved by a correspondingly large gate surface of the cross-coupled transistors in the read amplifier.