300+ TOP Digital Electronics Interview Questions and Answers

Digital Electronics Interview Questions :-

1. What do you mean by jitter?

The short term variations of a signal with respect to its ideal position in time. It is also defined as variation of clock period from edge to edge.

2. What is the difference between bit, nibble, byte and word?

A bit is a single binary digit, a nibble is a combination of 4 binary digits, a byte is a combination of 8 binary digits while a word is made up of several bytes.

3. What is the main difference between Harvard architecture and Van-Newmen architecture of computer?

In Harvard architecture model, separate data and instruction memory was used which makes it faster whereas in Van-newmen architecture, model instructions and data were stored in single memory. So this model was simple but slow.

4. What are the characteristics of Flash memory?

The characteristics of Flash memory are-

  • It is a special type of RAM.
  • It is a non volatile memory which is powered continuously.
  • The erasing and programming of this memory takes place block by block.
  • Due to this process, the flash memories are faster than EEPROMs which erase and write new data at byte level.
  • Important features of a flash memory are high speed, low operating voltages. Low power consumption and durability.

5. What is CAM?

CAM is called as content accessible memories. It is a special type of RAM. It can perform association operation in addition to the read/write operations performed by the conventional memories.

6. Which diode is used in HTL logic circuit to increase noise immunity?

HTL possesses highest noise immunity. In HTL logic circuit zener diode is used in place of normal diode to increase noise immunity.

7. What are the characteristics of Ring counter?

The characteristics of Ring counter are-

  1. With n flip flops, there are n-states present in ring counter.
  2. With n flip flops, maximum count possible in Ring counter is (2n-1).
  3. Decoding is very easy in Ring counter, because there is no aid of extra circuit.

8. What is MOD number?

The MOD number indicates the number of states in counting sequence. It indicates the frequency division obtained from the last flip flop.

9. What is lock out condition in counters?

A counter is supposed to follow the sequence of only the desired states. If it enters into an unused or unwanted state, then it is expected to return back to a desired state. Instead if the next state of an unwanted state is again an unwanted state then the counter is said to be in the lockout conditions.

10. Which shift register is used to convert temporal code into spatial code and vice versa?

To convert temporal code into spatial code, we use SIPO register while to convert spatial code to temporal code, we use PISO register.

Digital Electronics Interview Questions
Digital Electronics Interview Questions

11. What is the difference between Moore and Mealy circuit?

  • The synchronous sequential circuit is called as a Moore circuit if the output depends only on the present state of flip flops.
  • The circuit is called as a Mealy circuit if the output is dependent on the present state of flip flops and the external inputs.

12. Which flip flop is called as universal flip flop?

JK flip flop is called as universal flip flop because the flip flops like D-FFs, SR-FFs and T-FF can be derived from it.

13. What are preset and clear inputs of flip flops?

In the flip flops, when the power switch is turned on, the state of outputs is uncertain. But this uncertainty cannot be tolerated in certain applications. In some applications it is necessary to initially set or reset the flip flops.

This can be practically achieved by adding two more inputs to a flip flop, called preset (PR) and Clear (CLR) inputs. These inputs are called as direct or asynchronous inputs because we can apply them any time between clock pulses without thinking about their synchronization with the clock.

14. What is the difference between Flip flop and Latch?

While gates had to be built directly from transistors, Latches can be built from gates and Flip flops can be built from latches. This fact will make it somewhat easier to understand Latches and Flip flops.

The difference between them are:

  • Latch is a combinational logic device while Flip flop is a sequential device.
  • Flip flop is a synchronous device while Latch is asynchronous device.
  • Latch does not have a clock signal whereas a Flip flop always does.
  • Latch is faster than Flip flop.

15. What is the advantage of using open collector output in TTL logic gates rather than using totem pole output?

With Totem pole output wired-And operation is not possible in TTL gates which may lead to transistor burning. With open collector output wired-AND operation is possible.

16. What do you mean by current hogging and which logic family has this problem?

Current hogging problem is due to different characteristics of transistor. Owing to these differences, the saturation voltages of the load transistors may be different. So when one transistor enters into saturation it will not allow other transistors to enter saturation and will take whole of the current supplied from the driver gate. This is known as current hogging. DCTL has the problem of current hogging.

17. How microprocessor works without internal memory?

Microprocessor consists of address, data and control buses with some internal registers to process the task through external memory.

18. Why look ahead carry adder is faster than ripple adder?

Look ahead carry adder is faster; since carry is generated in parallel at all the stages of addition rather than sequentially as in ripple adder.

19. What is the difference between compiler and interpreter?

  • Compiler- Programs that converts English like words of a high level language into the machine language of a computer. It needs a given program called source code and translates the program into the machine language, called object code.
  • Interpreter- It translates one statement at a time from a source code to an object code.

20. Which code is called as minimum change code and why?

Gray code is called as minimum change code because it has a very special feature that only one bit will change, each time the decimal number is incremented.

21. What is the difference between digital signal and binary signal?

A digital signal is defined as a signal which has only a finite number of distinct values. Digital signals are not continuous signal, they are discrete signals.

If a digital signal has only two distinct values, i.e. 0 and 1 then it is called as a binary signal.

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