RTL AND gate
RTL means transistor-resistor logic.
Since we just finished making an RTL OR gate, you might be wondering if there's any reason why couldn't make an AND gate using RTL. There isn't and this Project proves it. You can see how this circuit operates by looking at the schematic.
You can see that both 2SC Transistors are connected in series, with the current from the collector of one going to the emitter of the other. Only when both Transistors are operating can the 2SA Transistor operate. The 2SA Transistor causes the LED to light, RTL digital circuits were among the first to be developed, but they are not used very often today.
One big problem is that slight changes in voltage can cause RTL circuits to operate improperly. Another problem is that only a small number of devices can be connected to an RTL circuit without affecting its operation.
Other digital circuits have been developed to overcome these problems. One is called DTL and we're going to look at it next. Can you guess what DTL stands for?
Make a mental guess because we're soon going to find out.