Write short notes on any two: (i) Schmitt trigger (ii) PLA (iii) Look ahead carry generator (iv) Karnaugh Map

(i) Schmitt Trigger:

A Schmitt trigger is a regenerative comparator circuit with hysteresis. It is a bistable multivibrator that produces a square wave output from an analog input signal. The Schmitt trigger has two threshold levels: an upper threshold (VT+) and a lower threshold (VT-). When the input signal exceeds VT+, the output switches to the high state. When the input signal falls below VT-, the output switches to the low state. The hysteresis prevents the output from oscillating when the input signal is near the threshold levels.

Applications of Schmitt Trigger:

• Schmitt triggers are used in a variety of applications, including:
  • Level shifting
  • Pulse shaping
  • Oscillators
  • Logic gates
• Schmitt triggers are particularly useful in applications where the input signal is noisy or has a slow rise or fall time.

(ii) PLA (Programmable Logic Array):

A programmable logic array (PLA) is a type of programmable logic device (PLD) that can be programmed to implement a variety of logic functions. PLAs consist of an array of logic gates that are interconnected by programmable metallization. The logic gates are typically arranged in a two-dimensional array, with the inputs to the PLA on one side and the outputs on the other side. The metallization is used to connect the inputs to the logic gates and the outputs to the external circuitry.

Advantages of PLA:

• PLAs are relatively easy to program.
• PLAs can be used to implement a wide variety of logic functions.
• PLAs are relatively fast.

Applications of PLA:

• PLAs are used in a variety of applications, including:
  • Digital signal processing
  • Data processing
  • Telecommunications
  • Industrial control

(iv) Karnaugh Map:

A Karnaugh map is a graphical representation of a Boolean function. It is a two-dimensional map, with the variables of the function on the axes and the values of the function in the cells. The Karnaugh map can be used to simplify Boolean functions and to identify common subexpressions.

Advantages of Karnaugh Map:

• Karnaugh maps are easy to use.
• Karnaugh maps can be used to simplify Boolean functions quickly and easily.
• Karnaugh maps can help to identify common subexpressions.

Applications of Karnaugh Map:

• Karnaugh maps are used in a variety of applications, including:
  • Logic design
  • Computer architecture
  • Digital signal processing