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Diffusion capacitance is the capacitance due to transport of charge carriers between two terminals of a device. - Amog This diffusion capacitance is due to depletion capacitance which is a function of forward bias applied to emitter junction of a transistor and due to diffusion capacitance which a function of transconductance of the transistor. Its value is 100 pF. Tirupanyam B.V
No, the voltage across a silicon PN junction diode does not depend exponentially on the current through the diode. The relationship between voltage and current in a PN junction diode is described by the diode equation, which is an exponential relationship between current and the voltage across the diode. However, this relationship depends on factors such as the temperature and doping levels of the diode, in addition to the material used.
The base of a transistor is basically a diode wich follows an exponential curve at very low level it display an almost infinite inpedance but at hi lelvel any additional diode current will not increase its voltage drop therefore a nominal value is assigned of .6v to .7v
The cut in voltage is that voltage where after the current increase rapidly and it's value is different-2 for different type of semiconductor. for silicon it is 0.7 and for germanium it is 0.3 volt. It means if you made a diode from silicon than applied voltage below 0.7 volt will not able to flow current (if flow than it is in term of few micro ampere) . it means diode will stay in off mode and for germanium same things will happen and it will rest on off condition below 0.3 volt(applied).
A: Actually it begins to conduct almost as soon as there available current. but the current is such a low value that it is considered not to be conducting at all. And the 0.7 volts drop is a chosen value to indicate that the diode is fully conducting and the voltage drop across is .7 volts there about. It can have any value lower then that and it all depends on the current flowing at the time.
space charge region in a diode or say a bjt for better understanding is same as the depletion region, both transition capacitance and depletion capacitance are the same c= (epsilon*A)/d ; where ... c is capacitance A is area and d is the depletion width the other type of capacitance is the diffusion capacitance c= (T*I)/(n*V) where ... c is the capacitance T is transition ti me I is the drift current n is emission coefficient ... its value is 1 for germanium and V is thermal voltage .. 26mv
0.3v as opposed to the silicon 0.6v
Short answer: By using a varactor diode as the capacitance in a parallel resonant ckt, by changing the reverse bias voltage you change the value of capacitance which in turn changes the resonant frequency. This makes a tuneable resonant ckt.
Diffusion capacitance is the capacitance due to transport of charge carriers between two terminals of a device. - Amog This diffusion capacitance is due to depletion capacitance which is a function of forward bias applied to emitter junction of a transistor and due to diffusion capacitance which a function of transconductance of the transistor. Its value is 100 pF. Tirupanyam B.V
Transition capacitance : A reverse biased PN-junction has a region of high resistivity (depletion layer) sandwiched in between two regions of relatively low resistivity. The P-N regions act as the plates of a capacitor and the depletion layer acts as the dielectric This is known as the transition capacitance or depletion capacitance. Diffusion capacitance : It is the capacitance due to transport of charge carriers between two terminals of a device like the forward biased PN junction. In a semiconductor device with a current flowing through it (for example, an ongoing transport of charge by diffusion) at a particular moment there is necessarily some charge in the process of transit through the device. If the applied voltage changes to a different value and the current changes to a different value, a different amount of charge will be in transit in the new circumstances. The change in the amount of transiting charge divided by the change in the voltage causing it is the diffusion capacitance. The adjective "diffusion" is used because the original use of this term was for junction http://www.answers.com/topic/diode, where the charge transport was via the diffusion mechanism.
Forward biase the given diode by using a Variable resistor in the circuit. By adjusting the value of variable resistor you will adjust the voltage being applied to junction diode. First adjust the resistance such that no(negligble) current flows through the circuit. Now start decreasing the value of resistance. Note the voltage across resistor(Vr) when current just starts flowing through the circuit. Then Potential barrier of diode will be: Vb=V-Vr Vb:Barrier Potential V:Battery Voltage Vr:Voltage Drop across resistance when current just starts flowing through the circuit.
If the meter is developing more than the necessary forward breakdown voltage of the diode, typically 0.7 volts, then the diode is bad. However, some meters do not generate enough voltage in resistance mode to bias the diode on, unless you flip a switch that enables diode test mode. Use another meter at the same time to measure the voltage across the diode and compare that with the diode's published forward breakdown voltage.
The question is not specific enough. I think you mean in a simple crystal radio, using a diode detector. The small value capacitance after the detector, takes any stray RF frequency down to earth, before being passed onto the headphones, where it would otherwise swamp the headphone coils.
No, the voltage across a silicon PN junction diode does not depend exponentially on the current through the diode. The relationship between voltage and current in a PN junction diode is described by the diode equation, which is an exponential relationship between current and the voltage across the diode. However, this relationship depends on factors such as the temperature and doping levels of the diode, in addition to the material used.
The base of a transistor is basically a diode wich follows an exponential curve at very low level it display an almost infinite inpedance but at hi lelvel any additional diode current will not increase its voltage drop therefore a nominal value is assigned of .6v to .7v
depends on circuit and its construction.
the current which has negative value n passes through the diode is called as diode reverse current