The present invention relates to SET/RESET latch circuit, Schmitt trigger circuit, and MOBILE based D-type flip flop circuit and frequency divider circuit using the SET/RESET latch circuit and Schmitt trigger circuit. Herein, SET/RESET latch circuit is especially configured with CML-type transistors and negative differential resistance diodes. The SET/RESET latch circuit can be applied for very high speed digital circuits
A SET/RESET latch circuit, characterized by including a transistor 1 and 2 in which each emitter of said transistors is commonly connected to a current source, and a negative differential resistance diode 1 and 2 which are respectively connected to each collector of said transistor 1 and 2; and additionally performing to be the relationship of IP<IEE<2·IP(where, IP: the peak current of said negative differential resistance diode 1 and 2, IEE: the current of the current source connected in series to the common node of emitters of said transistor 1 and 2); and thereby providing a single and differential Non-Return-to-Zero mode outputs in case that Return-to-Zero mode SET and RESET voltages are respectively supplied on the base ports of said transistor 1 and 2.