This chapter discusses VLSI circuits and approximate computing, which are the upcoming fields in VLSI design. This chapter focuses on Tunable Memristor emulators. This is a CNFET based tuneable memristor emulator. It also discusses a VDTA based robust electronic lead tunable memristor emulator circuit along with methods that focus on analysis and characterization of leakage reduction. A multi bit soft error immune SRAM cell for low power application is also discussed in this chapter using BitMAC. Along with these a bit serial computation based efficient multiply accumulate unit. For a deep neural network accelerator is discussed. Design of low power multiplier with less area using quaternary carry. Incremental adder for newfangled processor. After that, an ultra-low power and fast voltage level shifter using Mullar C-cell for VLSI system is also discussed.