In this paper,We design circuits which base on negative-differential-resistance(NDR) devices,NDR device is composed of metal-oxide semiconductor field effect transistor (MOSFET) and hetero junction-bipolar-transistor(HBT)。N NDR devices are connected in series or parallel,they show the folding I-V characteristics which have N peaks and N valleys。The folding I-V characteristics can reduce the number of devices which will be used and complexity。We are interesting in the multiple-valued logic circuit。