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Electronics Engineering
Electronics Engineering is a branch of engineering that deals with practical applications of electronic components, devices, systems, or equipment. Electronics are devices that operate on low voltage sources, as in electron tubes, transistors, integrated circuits, and printed circuit boards and use electricity as part of its driving force.
24,372 Questions
What is the Use of clock in flip flops?
The primary use of a clock in flip flops is to provide the trigger pulse to the flip flop
A digital instrument is a instrument whose out put is in discrete form.
SMD is an abbreviation for Surface Mounted Device.
SMD's take up less space on a circuitry board. Smaller components and smaller size of consumer electronics makes it easier to sell and use electronics where it previously was thought difficult.
As components shrink in size, they might also use less electricity (current). They may work faster and as size is smaller, the cost of mass-production is significantly smaller.
SMD's are however more at risk regarding Electromagnetic discharges as in EMP (Electro Magnetic Pulse) most commonly known from detonations of nuclear devices in the atmosphere. Such an EMP will in most cases render SMD electronic devices useless, where as older more sturdy electronics might survive depending on the proximity to the origin of the discharge.
Why intermediate frequency transformers are used in modulation process?
They are used as adjustable bandpass filters in superheterodyne (Google it) recievers. They determine how well you can select the radio station you require, while rejecting those close to it. They work in a fixed frequency range where their characteristics can be optimised.Very many modern radio recievers use some form of the superheterodyne principle though the function of the IF Transformer (ie bandpass filter) can be realised digitally, as in mobile phones for example. For AM radio a bandwidth of 9 KHz at 450KHz is typical.
The NPN transistor when used as an amplifier is operating in linear mode, and, when operating as a switch, in saturated mode.
In the following discussion, base currrent means base-emitter current, while the base is more positive than the emitter, and collector current means collector-emitter current, while the collector is more positive than the emitter. There is base-collector current, but we are going to ignore it for now - besides, we are going to discuss class A, common emitter, configuration.
The PNP transistor is very similar. Everything is backwards, including Vcc, which is now -Vcc, or appropriate reconfiguration. The rules are the same - just backward.
In switched or saturated mode, the ratio of base to collector current is far greater than beta-dc, or hFe, so the transistor is operating way out of its linear mode. We call that saturated mode, and the transistor is essentially either fully on or fully off, and therefore operating as an on-off switch.
The rest of this discussion will focus on linear or amplilfier mode.
If the ratio of base to collector current is less than beta-dc, or hFe and, if both base and collector voltage are greater than cutoff voltage, then the transistor is operating in linear mode. Well, sort of, for best linear mode, we look at the data sheet, or make empirical observations, and we pick the base and collector currents that are centered between the base knee and the collector knee, i.e. "in the middle of" the linear region.
In this mode, a very small base current can control a much larger collector current, and, most importantly, a very small change in base current can create a much larger change in collector current.
In the theoretical case, for example, where the emitter is grounded and where hFe is 100, then 1 mA of base current translates to 100 mA of collector current, and 2 mA of base current translates to 200 mA of collector current. Problem is, that hFe varies amongst even so called identical transistors, and hFe varies as a function of temperature as well.
So, in the practical case, an emitter resistor is added to stabilize the transistor and place limits on the need for hFe of a particular value. Done properly, this will yield predictable gain for various transistors and for various temperatures.
Now, lets look at how gain works in the practical sense. The base voltage is also a known delta above emitter voltage. Yes, temperature will affect this, but proper design can make this a negligable factor. The emitter current times the emitter voltage results in a known voltage. By Norton's current law, the base current and the collector current add up to be the emitter current, but by hFe, the base current is very much smaller than collector current, meaning that the really important part is that collector and emitter current are the same for all practical purposes.
So, now add a collector resistor. Ignoring base current, the collector/emitter circuit is a series circuit, and Norton's current law, reinterpreted for series circuits, says the two resistors have the same current. Think about what that means; if the current in both resistors is the same, then the ratio of the voltage across the two resistors is proportional to their value. The gain of the amplifier is collector resistor divided by emitter resistor. That is critical knowledge. Again, base current enters into the equation but, if hFe is high enough, it does not matter.
All that is left, then, is to bias the base. You want to pick a base voltage (current) that places the collector current in the center (or in an appropriate point) of the linear region. Choose a nominal hFe, divide by collector current, and you get an approximation of what base current bias should be. Choose a resistor divider to match, keeping in mind that the two resistors (base to Vcc and base to Gnd) in parallel will reflect your effective input impedance.
Review everything, particularly your power levels. To calculate the power through the collector/emitter junction subtract collector resistor voltage from emitter resistor voltage from Vcc, and you get collector/emitter voltage. Multiply that by collector current, and you get power dissipated by the transistor in nomial bias condition.
Play with the values until you have what you want. You could even set this up in a spreadsheet.
Last, but not least, there is a base bias voltage. If you are going to amplify something, you need to maintain that nominal bias voltage. Connect a series capacitor between the base and the input point and you will be able to operate from an AC signal that is zero referenced. Just pick the RC time constant appropropriate for your application.
Similarly, there is a collector bias, so, if you want an AC output zero referenced, use a series capacitor also in between the collector and the ouput.
This is an AC coupled, inverting amplifier. There are DC coupled non-inverting versions, but they are more complicated, requiring more than one transistor, and this answer does not address them. Good luck!
No, 200mA is not the same as kilohms.
Amperes is a unit of current flow. Ohms is a unit of resistance. Other than being related by Ohm's law - Voltage = amperes x ohms - the two units are not the same.
3 dB is a change in power by a factor of 2. If it is plus, i.e. +3dB, power is doubled. If it is minus, i.e. -3dB, power is halved.
6 dB, then is a factor of four, or quarter; 6 dB is a factor of eight, or eighth, etc.
The actual equation is 3 log2 (POWER OUT / POWER IN).
How do you convert NTSC signal into a computer signal?
The best way to convert an NTSC signal into a computer signal is with a TV Frame Grabber. Buy the board, install it, and it should be able to convert NTSC video into MPEG or some other video. You will even be able to do this from RF, off the air or off of cable - just understand that some countries are digital, instead of analog - but this answer is NTSC, which is analog.
If you want to build the board yourself, consult the specifics of NTSC with google, wikipedia, or something - it is a complex task. In high level generalities, the process is...
Build a sync separator that can differentiate between horizontal and vertical sync, and maintain the black and white reference levels.
Build an interlace detector that can detect and process the equalization pulses that occur during vertical sync. These equalization pulses are used to identify the interlacing between 29.97 Hz frame rate and the 59.94 Hz field rate.
Build a 3.58 MHz chroma oscillator that is phase locked to the chroma burst on the back porch of the horizontal sync.
Scan the data portion of each horizontal line - you will need a hardware array for each bit cell...
The luminance (black and white) data is the mean voltage between black and white reference levels at each bit cell.
The color saturation data is the amplitude of the 3.58 Mhz subcarrier at each bit cell.
The color hue data is the phase angle of the 3.58 MHz subcarrier at each bit cell.
You will need to convert the stream of bit cell data into video pixels, and then convert that into whatever PC compatible format you want.
Other things, such as closed captioning can be added by decoding the bit stream on various lines reserved for that during vertical sync.
Again, buy the board - its easier - unless you want to make a semester project out of this.
Yes, SiO2 is used for isolation and it can be grown easily when compared to other materials. The process is also simple as it only required oxidation of the already existing Si layer
Explain why the parts of your model are like the real circuit components?
It is because there is a light bulb and things like that......
High AC voltages are usually measured with?
They are usually measured using potential transformers that lower the voltages so that normal metering equipment can be used. Potential transformers PT's are almost no different that regular transformers except they are designed to be extremely accurate since they are used for metering purposes.
How can I check IC good or not?
This depends on the IC. Visual inspection will only go so far. You will need to test it and compare the testing to the datasheet; if it is not testing as specified in the datasheet, then it is bad.
Sorry, there's no one easy answer for all IC's.
What angle is the voltage increasing at its fastest rate?
This is a simple derivation problem. Take the derivative of the AC voltage waveform (I'll assume sin (t)), and set the derivative equal to the maximum value it can attain (which is 1):
cos (t) = 1, t = 0 degrees, thus for an AC waveform of y = sin(t), the fastest increase in voltage occurs at 0, 360, etc. degrees. The fastest decrease in voltage will occur at 180, 180 + 360, etc. degrees.
Negative feedback is most like?
Taking a step, feeling yourself imbalanced, and compensating by shifting your weight on the fly in order to maintain balance. You could simplify it further by saying that even just standing still requires a negative feedback loop in order to stay standing.
Why should you discharge the capacitor before measuring the capacitance?
If you don't it could fry your equipment. A capacitor can hold a charge for anextremely long time even years depending on the physical size and capacitance. It can hold a strong enough charge to kill.
Why is the number of turns in primary coil more than that of the secondary coil?
The number of turns or windings of a transformer can vary. There can be more in the primary, or more in the secondary, or there can be an equal number in a transformer that is simply used for isolation (an isoformer). More turns in the primary than secondary will create a step down transformer. More turns in the secondary are found in a step up transformer. The transformers on power poles have more turns in the primary to step the line voltage down for delivery to residential customers.
What is the significance of operating point in transistor?
Basically, a Q-point of any device gives information about the operating current & voltage of that particular device..This would help us to know about the max. & min. current or voltage upto which the can be operated safely.
What is the function of Substrate in MOSFET?
it will control the flow of electrons between the source and drain,the controlling will be depends upon the input voltage to the substrate.
What is the advantages of buffer circuits in digital electronics?
buffer circuits helpful in overcoming the impedance matching problem.for example if we want to send a signal from one devise to other ,if there is no impedance matching between this two then signal is not transfered.now if we use buffer in between these two devises then the buffer without changing the signal shape or value it simply transffers the signal
What is the bandwidth of a signal that ranges from 40KHz to 4 MHz?
Solution
Let fh is the highest frequency and fl is the lowest frequency.
Bandwidth = fh - fl = 4000 - 40 KHz = 3960 KHz = 3.96 MHz
How are the capacitors treated in the dc equivalent circuit of an amplifier?
In dc equivalent circuit of an amplifier all capacitors are replaced by open circuit because capacitor block dc.
As ,
Xc=1/2πfC
We know that that frequency of dc is zero so Xc will infinite so we replace all capacitors with open circuit.
