Miscellaneous (Logic Families) : MCQs & PYQs with Explanation

Option B

In digital electronics, different logic families vary in terms of speed, power consumption, and noise immunity. CMOS (Complementary Metal-Oxide-Semiconductor) is known for minimum power dissipation because it uses both PMOS and NMOS transistors in such a way that current flows only during switching, not in steady state.
In contrast, TTL (Transistor-Transistor Logic) and ECL (Emitter Coupled Logic) consume more power because current continuously flows through their circuits even when not switching.

Option B

JFET stands for Junction Field Effect Transistor. It is a unipolar device because its operation depends on only one type of charge carrier.

• In an N-channel JFET, current flows due to electrons only.
• In a P-channel JFET, current flows due to holes only.

Since only one type of carrier takes part in conduction, it is called a unipolar device.
A Bipolar Device is an electronic device in which both electrons and holes participate in current conduction. For example, a BJT (Bipolar Junction Transistor) is called bipolar because it uses both types of charge carriers.

Option A

A logic family is a group of digital circuits designed using a particular type of electronic components and technology. DCTL is one of the transistor-based logic families used in digital electronics. The full form of DCTL is Direct–Coupled Transistor Logic.
In DCTL circuits, transistors are directly connected without using coupling resistors or capacitors between stages.

Option D

Bipolar:

• RTL (Resistor-Transistor Logic)
• DTL (Diode-Transistor Logic) 
• TTL (Transistor-Transistor Logic) 
• ECL (Emitter-Coupled Logic) 
• IIL (Integrated Injection Logic)

Unipolar:

• NMOS (N-type Metal Oxide Semiconductor) 
• PMOS (P-type Metal Oxide Semiconductor) 
• CMOS (Complementary MOS)

Note:

Bipolar families use BJTs (Bipolar Junction Transistors), while unipolar families use MOSFETs (Metal-Oxide Semiconductor FETs) as switching devices.

Option D

FET (Field Effect Transistor) is widely used as a switching element in digital electronics. The most popular logic family using FETs is CMOS (Complementary Metal Oxide Semiconductor).