Abstract: Transistor is the major invention in electronics field, vacuums tubes are used in older times. But vacuum tubes have lot of drawbacks when comparing with transistor like their large size high power consumption etc. So transistor will easily replace vacuum tubes because transistors are small size, low power consumption cheap etc. but transistor can't completely replace these vacuum tubes because transistor can't work In high frequency application and also transistor will almost hit its minimum size further reduction in size is not easy so need a better replacement. Nano size vacuum tubes are better option.