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The input impedance of a current shunt feedback amplifier is the open loop impedance of the amplifier divided by 1+(A*beta)
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Techniques required for increasing the input impedance?
...of what? to a house, to a breaker (to lower fault current level?), to an amplifier circuit?
What is input impedance of fet amplifier?
Zin=Vds/Id [Vds=drain to source voltage ; Id = drain current]
Why input impedance of operational amplifier is infinite?
Input impedance (Zin) is assumed to be infinite to prevent any current flowing from the source supply into the amplifiers input circuitry. Infinite Input impedance is one of the Ideal Characteristics of the Op-Amp. With an assumption of Infinite Input impedance, there is no Loading on the preceeding stage to the Op-Amp (i.e. Supply.) or The Op-Amp under test does not draw any current from the I/p Supply to it's internal Circuitry.
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 typical values of input impedance and outoput impedance of ce amplifiers?
Output of the power amplifier is smaller 0.1 ohms and input of the loudspeaker is more than 4 ohms.
Why do you use feedback?
The voltage gain,input impedance,output impedance,bandwidth etc. are the characteristics of amplifier's. these are more or less constant for a given amplifier. These parameters are required to be controlled. This can be done by using feedback that's why we use feedback.
What is current series feedback?
The current series feedback is a negative feedback in which the output current feeds back a proportional voltage back to the input terminals in series with the input signal. Here the output impedance as well as the input impedance increases as both are connected in series.
What is the theory of voltage series feedback amplifier?
In a Voltage Shunt feedback Amplifier, the feedback signal voltage is given to base of transistor in shunt through a feedback resistor.This Shunt connection decreases the input input impedance and voltage feedback decreases the output impedance. In this amplifier input is current and output is voltage. Thus Transresistance is stabilized.Input and Output impedances are reduced by a factor of 'D'(desensitivity factor). Advantages: 1)Gain independent of device parameters. 2)Bandwidth increases. 3)Noise and non-Linear distortion decrease. 4)Prevents Loading effect. 5)Acts as good source for the next stage.
Advantages of negative feedback amplifier?
Most practical amplifier circuits use negative feedback for the following practical benefits: Stabilization of voltage gain, decreasing output impedance, increasing input impedance, decreasing distortion, increasing bandwidth.
Input impedance of voltage amplifier?
In audio the input impedance of an amplifier is between 10 kiloohms and 20 kiloohms.
What is the simplest way to convert capacitance to voltage?
If it is a variable cap, apply AC signal to the capacitor as per its specifications.This is done because the variation in the voltage gives a corresponding current output due to the charging and discharging of capacitor. Then a Trans-impedance amplifier can be used to convert this input current to voltage. Current amplifier can be used to amplify the current at the input of the trans-impedance amplifier. Similarly a voltage amplifier can be used at the out put of the trans-impedance amplifier to amplify the voltage output.
In a multistage amplifier input impedance is high and output impedance is low justify the statement?
no. input impedance is low & output impedance is high
Techniques required for increasing the input impedance?
...of what? to a house, to a breaker (to lower fault current level?), to an amplifier circuit?
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
What is input impedance of fet amplifier?
Zin=Vds/Id [Vds=drain to source voltage ; Id = drain current]
Difference between transistor and vacuum tube?
They are both used for similar functions, such as oscillators, amplifiers, and switches. The vacuum tube was invented first, and has therefore been around longer than the transistor.
What is vector impedance meter explain with circuit diagram?
A vector impedance meter is used to measure impedance and phase angle, this is done by calculating voltage and current through an impedance and then calculating Z and phase angle with that, now there are two modes for operation i.e constant current mode and constant voltage mode. CONSTANT CURRENT MODE construction = first of all there is a wien bridge oscillator(w) to choose frequency then an AGC amplifier(a) to regulate current then a z switch control(zs) which regulates gain of AGC amplifer, feedback to AGC amplifier is done by an dc differential amplifier(dc) dc | | | w--------->a--------->z now there is an ac differential amplifier too(ac) which gets one input from the z switch and one from the unknown impedance(imp), and there is a transconductance amplifier too which gets one of his input from the unknown impedance dc<------------------------------------------- | | | | | | w--------->a--------->z----------->ac-------------|------------> z meter | | | | | | _____| | | | | | | | | | | | imp | | | | | |________|___>rt___>| working---> in constant current mode we have to maintain constant current through impedance so current is made to come to unknown impedance from z switch, then that current goes through trans-resistance amplifier, which converts that current to a voltage that is sent to a dc differential amplifier and is compared with a reference voltage in dc differential amplifier then the difference between voltages is amplified and sent to AGC amplifier, so AGC together with z switch this way maintains constant current through unknown impedance, now for calculation z-magnitude, ac differential amplifier gets input from unknown impedance and z switch, so difference is amplified and sent to a band pass filter which filters out then the filtered signal is sent to a z-magnitude meter which is calibrated to read z directly.
