Transistors and Combinational Logic Flashcards
What types of storage elements are used in sequential logic?
- Latches
- Flip-flops
- Registers
What roles do inputs and outputs play in logic circuits?
Inputs are the values fed into a circuit, while outputs are the resulting values produced by the circuit’s logic
What is the function of a multiplexer (MUX)?
MUX selects one input out of several inputs to connect to the output based on control signals
How can we create a NAND gate using CMOS technology?
By combining n-type and p-type transistors in a specific configuration to achieve the NAND function
How do we construct basic logic structures using MOS transistors?
By combining individual MOS transistors to form logic gates that implement simple Boolean functions
How does an n-type transistor operate compared to a p-type transistor?
An n-type transistor conducts when a high voltage is applied to its gate, while a p-type transistor conducts when the gate is at 0V
How is a decoder implemented in combinational logic?
A decoder takes n inputs and produces 2^n outputs, with exactly one output being true for each input combination
What distinguishes sequential circuits from combinational circuits?
- Sequential circuits have memory elements and their output depends on both current and previous inputs
- Combinational circuits rely only on current inputs
What is the importance of having a closed circuit for electron flow?
A closed circuit allows electrons to flow; without it, the circuit remains open and non-functional
How do we implement a logic function using a PLA?
By programming the connections from AND gate outputs to OR gate inputs based on the desired logic function
What are the two types of MOS transistors?
n-type and p-type MOS transistors
What is the purpose of a full adder in binary addition?
A full adder computes the sum of three bits: two significant bits and a carry bit, producing a sum and carry out
How does the truth table of a full adder work?
The full adder truth table shows all combinations of inputs and their corresponding sum and carry outputs
What is the logical function of a NAND gate?
The NAND gate outputs false (0) only when both inputs are true (1); otherwise, it outputs true (1)
How many control bits are required for a MUX with N inputs?
A multiplexer with N inputs requires log2(N) control bits
What is CMOS technology and how does it utilize both n-type and p-type transistors?
CMOS technology uses both n-type and p-type transistors to create efficient and low-power logic gates
What is the function of the R-S latch in digital circuits?
An R-S latch stores a single bit of information and has two control inputs, Set (S) and Reset (R)
What is the function of the gate in a MOS transistor?
The gate controls the connection between the source and drain; applying voltage can either allow or stop current flow
What are the basic building blocks of combinational logic?
Basic building blocks include decoders, multiplexers, full adders, and programmable logic arrays (PLAs)
How do transistors act as switches in circuits?
Transistors control the flow of electrons, allowing for information flow similar to how a switch controls electrical circuits
What is a programmable logic array (PLA) and how is it structured?
A PLA consists of an array of AND gates followed by OR gates, allowing for flexible implementation of logic functions
Why are simultaneous S and R inputs of a latch forbidden?
Simultaneous S and R inputs can cause metastability, leading to unpredictable behaviour of the latch outputs
Buffer logic gate
If the input is 1, then the output is 1; if the input is 0, then the output is 0
AND logic gate
Output is 1 only when both inputs are 1
OR logic gate
For the output to be 1, at least one input must be 1
XOR logic gate
Output is 1 if the inputs are different but 0 if the inputs are the same
Inverter or NOT logic gate
If the input is 1, then the output is 0; if the input is 0, then the output is 1
NAND logic gate
AND gate with the circle of a NOT gate at the output, output is false if both inputs are true, otherwise, the output is true
NOR logic gate
A combination OR gate followed by an inverter; its output is true if both inputs are false, otherwise, the output is false
XNOR logic gate
XOR gate followed by an inverter; its output is true if the inputs are the same and false if the inputs are different
