What is Diode Transistor Logic (DTL) Circuit?

Diode Transistor Logic (DTL) is also a saturated logic and uses diodes, resistors and transis­tors. The circuit diagram is shown in Fig. 47.2. The ba­sic DTL logic circuit is the NAND gate.

Diode Transistor Logic (DTL) Circuit

When inputs to all the three diodes are high, neither diode conducts and the tran­sistor is turned on by the cur­rent provided by VCC through R1 and output is, therefore, low. If either or all inputs are low, the associat­ed diode will conduct, the transistor will turn off and output is, therefore, high. It is seen that output is low only when all the inputs are high.

The family is characterized by (i) limited operating speed, (ii) fan-in of 8, (iii) fan-out of 5, (iv) low power consumption (v) poor noise immunity and (vi) highly temperature sensitive to threshold voltage.

As already mentioned, this technology has also become obsolete now.