0
If you mean JFET, it is because the gate junction is reverse biased.
Wiki User
∙ 11y ago
Add your answer:
Earn +20 pts
Why input impedance should be high for an amplifier?
The best way to answer this question might be to consider the consequences if the input impedance was low: with a low input impedance, (signifficant) current would start flowing, and the amplifier would draw energy from the signal sources. None of the typical signal sources is designed to deliver energy on its outputs (after all, this is where the amplifier itself comes in). It is certainly possible to think that some of these sources might be changed to deliver some energy, but this is not the case with present-time tuners, CD players, microphones, and so forth. Assuming that the energy supply was not the issue, just to ponder this theoretical scenario a little further, the fact that current would flow from the source to the amplifier would also make the signal more vulnerable to the characteristics of the cable that connects the two. The high impedance of an amplifier input draws no energy, thereby avoiding these issues. It is the amplifier's task to convert a very low energy, voltage-driven signal into an higher energy output signal (driving the speakers which themselves have a very low impedance). ---- The way I typically think about this is to consider connecting a load to a Thevenin equivalent circuit [1]. The voltage across the load is given by the voltage divider formula (Vload = Vsrc * Rload/(Rload+Rthevenin)). If there is a very low load impedance--this means the amplifier has a very low input impedance--most of the source voltage will drop over the Thevenin equivalent resistance. With a very high input impedance, however, the majority of the signal voltage will be transferred from the source to the load because in the above equation, if Rload >> Rthevenin, Vload is approximately equal to Vsrc. if an amplifier has low impedance input the f/b must be low impedance also which make it in practical to use. The hi impedance of a typical amplifier is because the input is one two diodes basically operating on it exponential curve. Making it virtual the same as the other diode. for a differential amplifier. Boltzmann constant will define the impedance of a single diode.
What are common uses of a common emitter amplifier?
bcause amplification factor beta is usually ranges from 20-500 hence this configuration gives appericiable current gain as well as voltage gain at its output on the other hand in the Common Collector configuration has very high input resistance(~750 kilo ohm) & very low output resistance(~25 ohm) so the voltage gain is always less than one & its most important application is for impedance matching for drivingh from low impedance load to high impedance source
Why input is voltage and output is current in fet?
The input is a Gate that is essentially infinite impedance, so no current. The output is essentially the resistance between Source and Drain, which controls the current flowing through it.
Why impedance relay is called as distance relay?
because the distance is propotional to the impedance of the line ,so the operation of the impedance relay comes into picture when the impedance seen by the relay is less than the pre-setting value.When a fault occurs ,the current increases to a high value and so the Impedence decreases and the relay actuates
What is the Difference between low and high impedance relays?
It depends on the resistance level in that area if the soil have low resistance then they will use high impedance system and vice versa..so reason behind this have to reduce fault current.
Why the input resistance of opamp is high?
Because op amp consist differential amplifier and they posses high input impedance so that op-amp also posses high input impedance.
Why a high input impedance?
A circuit (an amplifier) typically has a high input impedance so that it does not unduly load the input circuit. Any such load could cause distortion, and that is generally not desired.
Which characteristics of Op-Amp is responsible for virtual ground?
The main parameter responsible for virtual ground of an Op-Amp is Input Impedance . Generally , for an Op-Amp it is very high . So , we can conclude that the characteristics of an Op-Amp responsible for virtual ground is high input impedance .
Why input resistance of voltage amplifier is infinity?
For the successful amplification of the input signal the opamp should have ideally infinite input impedance . It should act like a buffer amplifierBUFFER amplifier--------------------->1.input impedance infinity2.output impedance zerothe reason is thatAny signal source will have source impedancefor the signal not to get lost and dropped across source impedance we ideally insert infinite impedance in series with it which makes the whole drop across the infinite impedance but not across the sourcesimilarly at the output zero impedance is used where in no part of the signal should be left behind in the op amp as a drop
Why input impedance should be high for an amplifier?
The best way to answer this question might be to consider the consequences if the input impedance was low: with a low input impedance, (signifficant) current would start flowing, and the amplifier would draw energy from the signal sources. None of the typical signal sources is designed to deliver energy on its outputs (after all, this is where the amplifier itself comes in). It is certainly possible to think that some of these sources might be changed to deliver some energy, but this is not the case with present-time tuners, CD players, microphones, and so forth. Assuming that the energy supply was not the issue, just to ponder this theoretical scenario a little further, the fact that current would flow from the source to the amplifier would also make the signal more vulnerable to the characteristics of the cable that connects the two. The high impedance of an amplifier input draws no energy, thereby avoiding these issues. It is the amplifier's task to convert a very low energy, voltage-driven signal into an higher energy output signal (driving the speakers which themselves have a very low impedance). ---- The way I typically think about this is to consider connecting a load to a Thevenin equivalent circuit [1]. The voltage across the load is given by the voltage divider formula (Vload = Vsrc * Rload/(Rload+Rthevenin)). If there is a very low load impedance--this means the amplifier has a very low input impedance--most of the source voltage will drop over the Thevenin equivalent resistance. With a very high input impedance, however, the majority of the signal voltage will be transferred from the source to the load because in the above equation, if Rload >> Rthevenin, Vload is approximately equal to Vsrc. if an amplifier has low impedance input the f/b must be low impedance also which make it in practical to use. The hi impedance of a typical amplifier is because the input is one two diodes basically operating on it exponential curve. Making it virtual the same as the other diode. for a differential amplifier. Boltzmann constant will define the impedance of a single diode.
How many ohms is the sending unit putting out?
Usually is the input impedance of the load 10 times higher than the input impedance of the sender. So the sender's ohms is one tenth of the load.
How does voltmeter loading affect a circuit being tested?
Meters are designed to have a high input impedance so that the circuit being tested is minimally affected.
How much voltage or current should be applied for impedance measurement to a human body?
Since the objective is to find out the impedance between two points, it is advisable to have a meter that has a high input impedance; the higher the better. This is because when the probes are applied across the "impedance" to be measured, the input impedance of the meter is effectively in parallel with the measured impedance. So, if the input impedance of the meter is infinite, the accuracy of measurement will be 100%. Now, let us take a look at the situation on the human body: If the 2 points for measurement are selected on the same acupuncture meridian, the impedance will be lower than if you select one point on the meridian and one point randomly on the other parts of the body. If you select 2 points (not on any meridian) randomly on the human body, the impedance will even be higher. If you are using electrodes with sticky pads for skin contact, the result will be different from that measured with acupuncture needles puncturing the 2 points. Hope this is helpful. K. Kit Sum.
Can nand be inhibitted or disabled?
I suppose so. If a three input NAND is used as a two input device, the third input can be viewed as an inhibit input. Also some NAND devices can be "3 stated" where the output goes to a high impedance.
What are common uses of a common emitter amplifier?
bcause amplification factor beta is usually ranges from 20-500 hence this configuration gives appericiable current gain as well as voltage gain at its output on the other hand in the Common Collector configuration has very high input resistance(~750 kilo ohm) & very low output resistance(~25 ohm) so the voltage gain is always less than one & its most important application is for impedance matching for drivingh from low impedance load to high impedance source
Answer What is the difference between output and input?
Input refers to data entered into a system, while output refers to the results produced by the system based on the input. Input is the information provided to a system, while output is the response or outcome generated by the system.
Why mosfet has insulated gate?
The SiO2 layer acts as an insulator and also it provides high input impedance to the MOSFET. This insulation is needed so that a circuit with high EMI or loads which generate back emf (motors) can be driven by applying gate current from a common circuit.
