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Why the voltage drop across LED is around 2V instead of 0.7V?
the binary semiconductors used to make LEDs have forward bias voltages from 1.5V to 6V depending on color (1.5V for IR-red to 6V for blue-UV) because the bandgap voltage of the semiconductor is higher than silicon. This higher bandgap is where the photons generated get their energy from. germanium has a lower forward bias voltage of 0.2V because the bandgap voltage is lower. metal-semiconductor contacts, like point contact diodes and schottky barrier diodes, can have forward bias voltages under 0.1V
What will be the output voltage if reference voltage is open circuited in a series voltage regulator?
unregulated voltage minus series regulator transistor drop.
What is bifference between optical bandgap and semiconduct0r bandgap?
we all know that electrons,photons, phonons can excite an electron from valence band to conduction band...i think the main difference between electronic bandgap and optical bandgap is that in electonic its the energy required for an electron to move from the valence band to the conduction band.but in optical bandgap photons(packet of energy in the form of light waves) are assisting the electrons to move from valence band to conduction band.The difference between optical and electronic bandgap is more complexe actually. The optical bandgap is the one that can be measured using optical techniques (based on transmission and reflection, i.e. Tauc plot). However, this measurement does not take into account all traps you might have within the bandgap that can modify the energy required to move one charge carrier from the conduction band ans the conduction band. The electronic band gap (which is the one of interest in fine, in an integrated device) is measured under operation. Thus, for many devices (lasers, solar cells...etc.) the electronic bandgap (energy required to get the device working) can defer from the optical bandgap.
What is the function of reference voltage?
A: Analogue and digital converters need a reference to weight the input related to the value of the reference. Other applications includes comparator switching and instrumentation
What is a circuit diagram of a voltage stabilizer?
It's a diagram showing the components and connections needed to build a voltage stabilizer. The diagram will show a power transistor and a voltage reference, such as a zener diode.
Why the voltage drop across LED is around 2V instead of 0.7V?
the binary semiconductors used to make LEDs have forward bias voltages from 1.5V to 6V depending on color (1.5V for IR-red to 6V for blue-UV) because the bandgap voltage of the semiconductor is higher than silicon. This higher bandgap is where the photons generated get their energy from. germanium has a lower forward bias voltage of 0.2V because the bandgap voltage is lower. metal-semiconductor contacts, like point contact diodes and schottky barrier diodes, can have forward bias voltages under 0.1V
Why zener diode is called reference diode?
They are frequently used to provide a voltage reference in voltage regulators.
What is importance of band gap in semiconductors?
bandgap has an importance role for conduction.if bandgap is max,the conduction of electron is min. and vice-versa.hence we can say that the bandgap desides the conductivity of any material(may be metal or nonmetal)
Can tubelight be operated as voltage reference?
no
What are the various uses of diode?
Most people think of diode as a rectifier. Fair enough, it is because an ideal diode is taught to be a rectifier. In fact most people like the ideal diode characteristic; but dislike the non-ideal characteristics of diodes. However, some of the important inventions of our time are based on non-ideal characteristics of the diode. Below are a couple of samples: 1) Temperature sensor. A diode voltage changes with temperature. Assuming a fixed current going through the diode in the forward biased region, and the current is low enough that the diode resistance does not affect the voltage, the forward voltage has a negative temperature coefficient of about -2mv/degreeC. Once the temperature and voltage relationship is characterized with a fixed current, one can tell easily the temperature from the reading of the forward voltage. 2) Bandgap reference and regulator. This is related to temperature sensing as well. Since diode voltage has a negative temperature coefficient, a positive temperature coefficient voltage component added to the diode forward voltage would make an excellent stable voltage reference; a voltage that is independent of temperature. Turns out, the forward voltage is not only a function of temperature, it is also a function of current. To make life more interesting, the temperature coefficient of the voltage voltage is a function of current. In other words, if you have 2 identical diodes with different current through them, the difference in these two forward voltages also changes with temperature. this voltage is: Vd1-Vd2 = (k*T/q) *ln( I1/I2) where I1 and I2 are currents through the 2 identical diodes. This voltage has a positive temperature coefficient and is directly propositional to T in degrees Kelvin. Utilizing this current, one can amplify and convert it into a voltage, adding this voltage to a diode voltage, you have the making of a bandgap reference. As it turns out, this current is also great for temperature sensor applications.
Advantages of silicon over germanium?
silicon has a wider bandgap than germenium .silicon jeakage current small, easily available then Ga and break down voltage is more. knee voltage of si is 0.7and Ga is having 0.3then Si is very useful.
How do you convert output voltage of thermocouple into temperature?
You need to know the temperature of the reference junction and the voltage difference between the reference and sensing junctions. First, you convert the reference temperature to a voltage using the reverse equation or table for your thermocouple type. Then you sum that voltage with the measured voltage. Finally, you convert the summed voltage back to a temperature using the equation or table for the thermocouple type you are using. If the reference junction is at zero degrees C, you can skip the reference summing part. Before computer processing was easy and cheap, the reference junction was often kept in an ice water bath for that reason.
What will be the output voltage if reference voltage is open circuited in a series voltage regulator?
unregulated voltage minus series regulator transistor drop.
What is bifference between optical bandgap and semiconduct0r bandgap?
we all know that electrons,photons, phonons can excite an electron from valence band to conduction band...i think the main difference between electronic bandgap and optical bandgap is that in electonic its the energy required for an electron to move from the valence band to the conduction band.but in optical bandgap photons(packet of energy in the form of light waves) are assisting the electrons to move from valence band to conduction band.The difference between optical and electronic bandgap is more complexe actually. The optical bandgap is the one that can be measured using optical techniques (based on transmission and reflection, i.e. Tauc plot). However, this measurement does not take into account all traps you might have within the bandgap that can modify the energy required to move one charge carrier from the conduction band ans the conduction band. The electronic band gap (which is the one of interest in fine, in an integrated device) is measured under operation. Thus, for many devices (lasers, solar cells...etc.) the electronic bandgap (energy required to get the device working) can defer from the optical bandgap.
What is a reference voltage of an adc?
The voltage at which the adc converts the signal.... it can also be called a limit of an ADC.
What is the definition of optical and electrical bandgap?
Optical bandgap means bandgap estimated using optical means or characterization. In simple words, let a light of different energies incident on the material. The material absorbs some energies and transmits some energies (the detector measures this). The threshold energy at which the material starts absorbing light is "Optical Bandgap". In a similar manner, electrical bandgap means bandgap estimated using electrical means or characterization. Here instead of measuring what light is observed of transmitted. You make electrical contacts for the material and measure the current instead of optical absorption. The incident light is of course absorbed, and carriers (electrons and holes) are generated in proportion to absorption. We measure current (nothing but charge which is proportional to absorption) and this current too shoots up at a threshold energy i.e. electrical bandgap.
Why as signal is usually grounded?
If meant ac signal then it is grounded so that the reference voltage is 0 & we get +ve voltage.
