ada paper

An Introduction to Digital Logic Families

What is a Logic Family?

In Digital Designs, our primary aim is to create an Integrated Circuit (IC).
A Circuit configuration or arrangement of the circuit elements in a special manner will result in a particular Logic Family.

What are the advantages of creating different Logic Families?

Electrical Characteristics of the IC will be identical. In other words, the different parameters like Noise Margin, Fan In, Fan Out etc will be identical.

Different ICs belonging to the same logic families will be compatible with each other.

Some Characteristics we consider for the selection of a particular Logic Family are:
Supply voltage range
Speed of response
Power dissipation
Input and output logic levels
Current sourcing and sinking capability
Fan-out
Noise margin
The basic Classification of the Logic Families are as follows:
Bipolar Devices
MOS Devices
Hybrid Devices Bipolar Families:
1. Diode Logic (DL)
2. Resistor Transistor Logic (RTL)
3. Diode Transistor Logic (DTL)
4. Transistor- Transistor Logic (TTL)
5. Emitter Coupled Logic (ECL) or Current Mode Logic (CML)
6. Integrated Injection Logic (IIL)
MOS Families:
1. P-MOS Family
2. N-MOS Family
3. Complementary-MOS Family
1. Standard C-MOS
2. Clocked C-MOS
3. Bi-CMOS
4. Pseudo N-MOS
5. C-MOS Domino Logic
6. Pass Transistor Logic Hybrid Family:
1. Bi-CMOS Family
Diode Logic
In DL (diode logic), only Diode and Resistors are used for implementing a particular Logic.Remember that the Diode conducts only when it is Forward Biased.

Disadvantages of Diode Logic
Diode Logic suffers from voltage degradation from one stage to the next.
Diode Logic only permits OR and AND functions.
Resistor Transistor Logic
In RTL (resistor transistor logic), all the logic are implemented using resistors and transistors. One basic thing about the transistor (NPN), is that HIGH at input causes output to be LOW (i.e. like a inverter).