Flip-flop electronic circuit

There is an electronic circuit called a flip-flop. It consists of two transistors connected in such a way that, if a voltage is applied, one side of the circuit becomes active and the other side not if a second voltage is applied, the circuit flips so that the active side becomes inactive and vice versa. Thus, just as with a conventional switch for which one touch puts it on and a second touch turns it off, one touch of the flip-flop turns it on and a second touch turns it ojf. Addition of two binary numbers now becomes possible. Suppose we want to add 2 -(- 1 (= 3 decimal). First, the numbers must be converted into binary code (10 and 01) and these become switch settings in the machine, but we need four switches so that 10 becomes on, off and 01 becomes off, on (Figure 42.6). 

First step towards synthesizing reversible molecular switches, and integrating these switches into an electronic circuits, had been done pioneered by Rotaxane-based-technology developed by HP. Any digital microelectronic device is based on memory elements and switches, set up as capacitors, diodes and transistors. Complex elements, such as bi-stable flip-flops, are created from these simple elements combining e.g. two transistor to set up a Schmitt trigger. 

---