Improved multipeak circuit with four-peak or live-peak current-voltage (I-V) characteristics of three series-connected negative differential resistance (NDR) devices are discussed and demonstrated. These novel phenomena occur only when these NDR devices satisfy certain relationships with respect to their electrical parameters. We will analyze and investigate these constraints in this paper. These characteristics could be applied to the multiple-valued memory or logic circuit with fewer devices in comparison with the traditional structure that stacks N identical NDR devices on top of each other to obtain N peaks in the combined I-V curve,