Digital Electronics

A multiplexer is a digital circuit that selects one of several input signals and forwards it to a single output. It is commonly called a data selector because it selects which data input to transmit. Data distributor, decoder, and encoder are different circuit functions.

Excess-3 code is a non-weighted code (each bit position doesn't have a fixed weight value) and it is self-complementing (the 9's complement is obtained by complementing each bit). Therefore it is both non-weighted and self-complementing. A weighted code assigns fixed weights to each bit position.

In sequential circuits (like flip-flops, counters), the output depends on both the present inputs and the present state (which stores past inputs). This memory of past states is what makes it 'sequential'. Combinational circuits depend only on present inputs.

ans 4

A decoder with N input lines can have up to 2^N output lines. If a decoder has 32 output lines, then 2^N = 32, which means N = 5 (since 2^5 = 32). Therefore, 5 input lines are required.

To convert binary to Gray code, start with the MSB (leftmost bit) which remains the same. Then each subsequent Gray code bit is the XOR of the current and previous binary bits. For 011010: MSB stays 0, then XOR(0,1)=1, XOR(1,1)=0, XOR(1,0)=1, XOR(0,1)=1, XOR(1,0)=1. Result: 010111.

Master-slave JK flip flop is specifically designed to eliminate the race-around condition by using two flip flops in a master-slave configuration. The master responds during the positive clock edge while the slave responds during the negative edge, preventing the output from changing multiple times during a single clock pulse.

Correct Answer: 3
2ⁿ = MOD,
Since we require to count till 5 (101), so 3 flip flops are required.

For 4-bit data 0111 with even parity Hamming code, the parity bits are calculated at positions 1, 2, and 4 (powers of 2). P1 covers bits 1,3,5,7; P2 covers bits 2,3,6,7; P3 covers bits 4,5,6,7. With data 0111 at positions 3,5,6,7, the parity bits are P1=0, P2=0, P3=0, giving the final code 0001111.

JK flip flop can function as a T flip flop when both J and K inputs are connected together (J=K). When J=K=0, the flip flop maintains its state (Q stays same). When J=K=1, it toggles (Q changes), which is exactly the behavior of a T flip flop where T=0 holds and T=1 toggles.

Demultiplexer performs the opposite function of a multiplexer - it takes a single input and routes it to one of multiple outputs based on select lines. This data distribution function gives it the name 'data distributor'.

Answer 1, since number of 1s is even.

A mod-10 counter requires 4 flip flops because the number of states is 10 (0 to 9). With n flip flops, we can represent 2^n states. For 2^3=8 < 10 < 2^4=16, we need 4 flip flops to accommodate 10 states, though 6 states will be unused.

Excitation table specifies the input conditions required for a flip flop to transition from its present state to the next state. Unlike a truth table that shows output for given inputs, an excitation table shows what inputs are needed to achieve desired state transitions.

A 4-bit down counter counts downward. When it reaches 0000 (the minimum value) and another clock pulse arrives, it wraps around to the maximum value 1111 (15 in decimal). This is the underflow behavior of down counters.

A four-variable logic expression has 2^4 = 16 possible combinations (minterms). A 16:1 multiplexer can realize any 4-variable function by connecting each minterm to the corresponding input line and using the 4 variables as select lines.

In BCD addition, when the binary sum exceeds 9 or produces a carry, adding binary 6 (0110) corrects it to valid BCD. This adjustment accounts for the 6 invalid BCD states (10-15) that are valid in binary but not in BCD representation.

PROM (Programmable Read-Only Memory) can be programmed by the user exactly once using a PROM programmer. During programming, fuses are blown to create the desired pattern. Once programmed, it cannot be reprogrammed - this is why it's called 'one-time programmable'.

PAL (Programmable Array Logic) has a programmable AND array followed by a fixed OR array. Users can program the AND gates to generate desired product terms, but the OR array connections are fixed at manufacturing time. This gives PAL its flexibility while keeping cost lower than fully programmable PLA.

Open collector output TTL can be used for wired-AND (also called wired-OR for negative logic) connections. Multiple open collector outputs can be connected together with a single external pull-up resistor, implementing the AND function. Totem pole outputs cannot be wired together due to potential short circuits.

Unipolar logic families use devices that rely on only one type of charge carrier (electrons or holes). MOS (Metal-Oxide-Semiconductor) transistors are unipolar devices as they use only majority carriers for conduction. BJT and IGBT are bipolar devices using both electrons and holes, while FET is a broader category that includes MOSFETs.

ECL (Emitter-Coupled Logic) is the fastest logic family because its transistors never saturate, eliminating storage delay. TTL and its predecessors like RTL and DTL have slower switching speeds due to saturation effects. ECL achieves nanosecond propagation delays at the cost of higher power consumption.

2's complement method converts subtraction into addition by representing negative numbers in a form that allows direct addition with the minuend. Unlike 1's complement which requires an end-around carry, 2's complement handles this automatically by discarding the final carry. 10's complement is for decimal systems.

Race conditions occur in asynchronous sequential circuits because inputs can change at different times and signals propagate through paths of different delays without a clock to synchronize them. Synchronous circuits use a clock to ensure all state changes occur simultaneously, eliminating race conditions.

T flip-flop toggles its output state on each clock pulse when T=1, making it ideal for toggle applications like frequency division. It's not a delay switch, simple switch, or general-purpose switching element - its primary function is toggling between two states.