Resistor-transistor logic
The resistor transistor logic , English resistor transistor logic ( RTL ), is a logic family from electronics that is no longer used today .
Logic gates and functions were implemented by linking resistors and then amplifying them with transistors . The output of these circuits can only control three inputs of other circuits, whereas the TTL gates have about ten. This maximum possible degree of branching is referred to as fan-out .
The RTL was the first form of digital electronic circuit , which was developed in the 1950s by Texas Instruments specifically for use in field seismics . The Massachusetts Institute of Technology (MIT) used this technology to design the Apollo Guidance Computer , which was used on board the Apollo spacecraft .
Circuit: 2 NOR with 3 inputs each (1965)
Picture of a dies: 2 NOR gates
construction
The circuit diagram on the right shows a NOR link with two inputs of type MC717 . It has a power loss P V of 5 mW and a running time t pd of 25 ns.
If a high level is applied to an input U 1 or U 2 , the corresponding transistor is switched on and the output is thereby switched to low level. A transistor is assigned to each input, the transistors share a common collector resistor R c . The output voltage U a therefore depends heavily on the load on the output, which results in a low fan-out. The transistors are switched in the saturated state because of the low-ohm base resistances R 1 and R 2 . As a result, the switching times are relatively long, but the arrangement is insensitive to sample variations of the transistors, since the transistors become conductive even with low amplification.
Because of the disadvantages described, RTL circuits are almost no longer used in industry.
See also
Other logic families are:
- Diode-transistor logic (DTL)
- Slow Fail-Safe Logic (LSL)
- Emitter-coupled logic (ECL)
- Complementary MOS Logic (CMOS)