Basic Slide of TTL, 7400 TTL Series,Two Input TTL-NAND Gate , Totem – pole Output Stage of TTL

1. TRANSISTOR TRANSISTOR LOGIC(TTL)
Submitted By Yogendra Yaduwanshi

2. 7400 TTL Series
o TTL ICs first developed in 1965 and they are
known as “standard TTL” . This version of TTL
circuit is not available now.
o TTL family use only transistor to perform the basic
logic operations.
o The standard TTL is improved to a great extent
over the year.
o TTL devices are still used as “glue” logic which
connects more complex devices in digital system.

3. Two Input TTL-NAND Gate
 The first, let us replace transistor Q1 by its equivalent
circuits.
 A and B are the input terminals.
 The i/p voltage A and B can be either low (zero volts
ideally) or High (+Vcc ideally).
 A and B both low : If A and B both are connected to
ground, then both the B-E junction of the transistor
Q1 are forward biased.

4. Totem – pole Output Stage of TTL
 The arrangement of Q3 and Q4 on the output side of a
TTL NAND gate is called the totem-pole arrangement.
 In this circuit, the three output component Q3,Q4 and
diode D1 are stacked one on the top of the other in the
form of totem-pole. At any time, only one of them will
be conducting.