Electronic and Communications Interview Questions - Part 6
What do you mean by 3 dB cutoff frequency? Why is it 3 dB, not 1 dB ?
3db implies 70%(o.7o7) of the power, i.e we are interested to consider the bandwidth range from peak to 70% because upto 70% its reliable. Hence 3db is called as half power freq. 3db value is the mean square value which is 70% of the maximum value.
What is meant by pre-emphasis and de-emphasis ?
Pre-emphasis "Improving the signal to noise ratio by increasing the magnitude of higher frequency signals with respect to lower frequency signals"
De-emphasis "Improving the signal to noise ratio by decreasing the magnitude of higher frequency signals with respect to lower frequency signals"
What is Race-around problem? How can you rectify it ?
A condition in logic network in which the difference in propagation times through two or more signal paths in the network can produce an erroneous output.in jk flip flop race around problem will occur when both the inputs are high. it can be prevented by using master slave jk flip flop
What is the basic difference between Latches and Flip flops ?
Latch works without clock signal,but works with a control signal and it is level triggered device. Whereas flip flop is a 1 bit storage element and works with a clock signal. It is a edge triggered device. Normally latches are avoided and flip flops are preferred.
What is Barkhausen Criterion ?
1./AB/=1,i.e. the magnitude of loop gain must be unity 2.the total prase shift around the closed loop is zero or 360 degrees.
what are active and Passive Components ?
ACTIVE COMPONENTS The components which produce the energy in the form of current or voltage are called as active components. Example: transistors etc,.
What is difference between Microprocessor and Microcontroller ?
Microprocessors generally require external components to implement program memory, ram memory and Input/output. Intel's 8086, 8088, and 80386 are examples of microprocessors. Micro controllers incorporate program memory, ram memory and input/output resources internal to the chip. Microchip's pic series and Atmel's AVR series are examples of micro controllers.
Why is Zener Diode always used in Reverse Bias condition ?
When biased in the forward direction it behaves just like a normal signal diode passing the rated current, but when a reverse voltage is applied to it the reverse saturation current remains fairly constant over a wide range of voltages. The reverse voltage increases until the diodes breakdown voltage V B is reached at which point a process called Avalanche Breakdown occurs in the depletion layer and the current flowing through the zener diode increases dramatically to the maximum circuit value (which is usually limited by a series resistor). This breakdown voltage point is called the "zener voltage" for zener diodes.
Define Analog and Digital Signal Processing ?
Analog signal processing is for signals that have not been digitized, as in classical radio, telephone, radar, and television systems. This involves linear electronic circuits such as passive filters, active filters, additive mixers, integrators and delay lines. It also involves non-linear circuits such as compandors, multiplicators (frequency mixers and voltage-controlled amplifiers), voltage-controlled filters,voltage-controlled oscillators and phase-locked loops. Discrete time signal processing Discrete time signal processing is for sampled signals that are considered as defined only at discrete points in time, and as such are quantized in time, but not in magnitude. Analog discrete-time signal processing is a technology based on electronic devices such as sample and hold circuits, analog time-division multiplexers, analog delay lines and analog feedback shift registers. This technology was a predecessor of digital signal processing (see below), and is still used in advanced processing of gigahertz signals.
The concept of discrete-time signal processing also refers to a theoretical discipline that establishes a mathematical basis for digital signal processing, without taking quantization error into consideration.
What is RS in RS-232 ?
RS-232 (Recommended Standard - 232) is a telecommunications standard for binary serial communications between devices. It supplies the roadmap for the way devices speak to each other using serial ports. The devices are commonly referred to as a DTE (data terminal equipment) and DCE (data communications equipment); for example, a computer and modem, respectively