Question

Explain the working of TTL NAND gate in detail.​

Answer 1

Explanation:

Transistor–transistor logic (TTL) is a logic family built from bipolar junction transistors. Its name signifies that transistors perform both the logic function (the first "transistor") and the amplifying function (the second "transistor"), as opposed to resistor–transistor logic (RTL) or diode–transistor logic (DTL).

Answer 2

Answer:

Demonstrates a TTL NAND gate with a totem pole output.   The    totem pole output implies that transistor T4 sits atop T3 in order to give low output impedance.  The low output impedance means a short time constant RC therefore the output can change rapidly from one state to the other. T1 is a multiple type emitter transistor. Such transistor can be thought of like a combination of various transistors along with a common collector and base. Multiple emitter transistors along with about 60 emitters have been developed. In this figure, T1 has 3 emitters thus there can be three inputs A, B, C. The transistor T2 functions as a phase splitter since the emitter voltage is out of phase along with the collector voltage. The transistors T3 and T4 by the totem pole output, the capacitance CL shows the stray capacitance and so on. The diode D is added to make sure that T4 is cut off while output is low. The voltage drop of diode D remains the base-emitter junction of T4 reverse biased therefore only T3 conducts while output is low.