You can arbitrarily get any functionality using transistors. Millions of transistors can be fabricated on a single chip to get highly complex functionality (Intel Core2duo,i3,i5,DSP processors). Transistors are small in size, consume small amount of power. If transistor is not there you will not have a smart phone having megapixel camera, built in modem, MP3 player, Wi-Fi, Video recording, GPS etc with battery back of many days. Transistor can amplify also.