Resistor Transistor Logic(RTL)

Now it is not used anywhere in the design of integrated circuits. In this type of ICs , only transistors and resistors are used.

The RTL circuits basically performs the NOR operation. Transistors either connected in series or parallel. The transistor works as switch.

A two input RTL circuit is shown below

The resistance is connected in the base and both input is applied to the base of both the transistor.

The collector end of both the transistor are joined together and connected to the output.

When the the input 1 to transistor T1 is high , T1 will conduct and making voltage at output zero.

Same happens when T2 conduct or both T1 and T2 conduct.

When no input is given means zero voltage , T1 and T2 both will be at cut off ( OFF) , and than output voltage will be equal to +VCC, making logic 1 .

RTL circuit parameters;

  • Propogation delay time : 12 nano seconds
  • Fan in :8, Fan out : 8
  • Noise : 0-2 volt
  • Power dissipation: 30-100 mW

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