What if transistors could have 3 states?
they can have three distinct states – active (conductive – saturated), off (non-conductive, off) and semiconductor (linear).
However, they are difficult to use, the three-state logic is not as common as binary.
There are several techniques for storing data using different discrete states, but they are prone to errors. even if they had more than 2 states, they had to be binary, otherwise we had to redirect all logical blocks, interfaces and techniques.
The only multi-state logic is the Qubit logic, where there is a cluttered state, but it is much more complex to understand unless you are a doctorate in physics. Transistors are analog devices. Digital circuits are only a particular type of analog circuit. you can theoretically define as many states as you want.
Whether they are practical or not is another question. would you have increased processing power with more states, perhaps. you will have to invent the calculations, something that goes beyond the Boolean algebra, but which resembles it. logic 1.0, -1 was proposed, but it never went very far. there was also a logic that seemed promising but also died.
Engineers and other digital designers have proposed logic based on such a device, in which the cc states are: yes, no, and maybe. they can be used to design a fuzzy logic! seriously, what other state can a single transistor take but, turn on, turn off, or transfer a resistor (which means amplify)? the term tri-state is a registered trademark capability to place logical gates in a high impedance, essentially non-factor state.
A transistor can already be used in a different number of regions, namely in the active and saturation regions when it is conducting and in the cutoff region when it is not conducting. Now, the reason why digital gates have two states is that, because the transistors are used in the saturation region (if we are talking about mosfets, they are actually in the active region).
If they were used in active regions, you could have many different output voltages using a push-pull configuration similar to that used in operational amplifiers, but the configuration has ceased to be digital.
More importantly, the power consumption would increase considerably, as it is now possible to have both conductive transistors.