5 ms·
Transistors are generally at their lowest static power dissipation if the are either fully on or off. The analog middle is great if you're trying to process con
by mikewarot 1y ago
Transistors are generally at their lowest static power dissipation if the are either fully on or off. The analog middle is great if you're trying to process continuous values, but then you're going to be forced to use a bias current to hold on in the middle, which is ok if that's the nature of the circuit.
A chip with billions of transistors can't reasonably work if most of them are in the analog mode, it'll just melt to slag, unless you have an amazing cooling system.
Also consider that there is only one threshold between values on a binary system. With a trinary system you would likely have to double the power supply voltage, and thus quadruple the power required just to maintain noise margins.
- foxglacier 1y agoWouldn't you also get data loss using the linear region of transistors? The output would be have some error from the input and it would propagate through the circuit, perhaps eventually reaching on or off where it would be stuck.
- throw10920 1y agoThis is great point, and I'll extend it by claiming that there's a more general physical principle underneath: that it's significantly easier to build bistable systems than tristable (or higher) systems, so much so that it makes up for the fact that you need more of them. This is far more general than electronic systems (e.g. quantum computers follow the same principle - it's far easier to build and control qubits than qutrits/qudits). (technically, it's even easier to build systems that have a single stable configuration, but you can't really store information in those, so they're not relevant)
- rini17 1y agoIt can be solved various ways, not only middle, electricity has negative voltages too. So you can have the third distinct "fully on" state at negative voltage. This isn't practical with silicon semiconductors but might be possible with other technology. The Soviet ternary computer Setun used custom ternary switches.
- theamk 1y agothere is nothing special about negative voltages, it's all relative to some point anyway. With mixed analog/digital circuits for example, it's pretty common to treat exactly same voltages either as -2.5/0/2.5 (relative to midpoint), or as 0/2.5/5 (relative to negative rail). What matters is having multiple treshold voltages with distinct behaviour. Setun used ferrite transformers which do have multiple thresholds (postive and negative fields) - but modern electronics, including transistors, does not.
- CoastalCoder 1y agoThis is 1000% not my area of expertise, but if we're imagining circuits where current can flow in different directions at different times, would diodes potentially become more interesting for logic?
- theamk 1y agoDTL, diode-transisor logic, was used in 1960-1970's when they did not have cheap high-quality transistors yet. The power consumption was pretty terrible, but you needed less semiconductors. In the modern logic, diodes are not that useful because transistors already react to one polarity only. You simply connect multiple transistors to same input, and the right ones will activate.
- rini17 1y agoDiodes have quite big forward voltage, like 0.5V, depends on current but in any case it means lots of wasted energy. FETs got highly optimized over time, can be switched on with only minuscule resistance and also can be miniaturized. Modern FETs are capable of switching spot welding currents without getting destroyed, while in thumbnail-sized package, imagine that. My grandpa was an electrical engineer and would be completely blown away by such a component.
- pezezin 1y agoIt is perfectly viable with silicon. The venerable Fast Ethernet used PAM3, as do USB4 and GDDR7, and Gigabit Ethernet uses PAM5.
- deleted 1y ago[deleted]