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What is effect of load on voltage gain of common emitter amplifier?
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∙ 11y ago
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∙ 11y ago
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What is the effect of Rs and RL on the voltage gain of an amplifier?
it reduces the gain
What is difference between early effect and punch through in BJT?
When we apply reverse bias voltage to input and output sides of a BJT, then the width of the depletion layer at emitter-base and base-collection got increased. Due to which the effective base width got decreased. This phenomenon of reduction in the base width is called Early effect. And if we go on increasing the Reverse bias voltage then at a time instant the width of the base becomes zero and this effect is called punch through effect and that reverse bias voltage is called punch through voltage.
Why to calculate the current gain in transistor?
A: Transistors are really voltage amplifiers since the effect is voltage across a load. Using beta as a means to calculate gain is an approximation. basically is the ratio emitter resistor and collector resistor with no loadNo. Transistors (bipolar junction types, what most people think of as "transistor") are considered to be current devices.Although it's possible to specify a transconductance (output current/input voltage), this has not been done since the earliest days of transistor theory, and you will have trouble actually finding a transconductance specification in data sheets.Current gain is (output current/input current).In a common emitter circuit, this is (collector current/base current), known as hfe or "beta", with ranges from as low as 10 for high-current devices to high hundreds for low-power audio types.In common base, it's (collector current/emitter current), and it's just a bit less than 1.0, typically 0.95 to 0.999. This is known as hfb or "alpha".In common collector, it's (base current/emitter current), known as hfc, with about the same values as hfe.The exceptions are the obsolete point-contact types of the 1950s/early 1960s, and the various types of field-effect/MOS devices known variously as FETs, JFETs, IGFETs and MOSFETs.The field-effect/MOS devices have very low/zero input current, so they are not specified for current gains.
How does a jfet input operational amplifier work?
A: an operational amplifier has two input A+ and a - input feeding to a base of a transistor ideally both diodes are matched with a current source to make them equal so basically they are both balanced or virtually at the same potential increasing one potential to one will inversely effect the other. usually these junctions are transistor base to emitter but it could that one is just a plain diode working on the exponential curve of the diodes
What effect does low impedance have on voltage regulation?
raised voltage output
What is the effect of no emitter resistance on common emitter amplifier?
Limit current through emitter, Often the resistance is the load itself. So the restatnce limits current on what otherwise would act as a voltage follower.
What is the effect of emitter resistance in common emitter amplifier?
The gain of a common-emitter amplifier is collector resistor divided by emitter resistor, or hFe, whichever is less. Since hFe depends on temperature, designing the amplifier to be dependent on resistance ratio makes it more stable. As such, the emitter resistance serves to stabilize the amplifier.
What is the effect on voltage gain in a common emitter amplifier when the decoupling capacitor is removed?
The emitter bypass capacitor, in a typical common emitter configuration, increases gain as a function of frequency, making a high pass filter. Removing the capacitor will remove the gain component due to frequency, and the amplifier will degrade to its DC characteristics.
What is effect of an unbypassed resistor on the common emitter amplifier circuit?
An emitter resistor in a common emitter circuit will cause the stage to experience the effects of degenerative feedback if it is unbypassed. The degenerative feedback reduces gain. This is probably the primary effect in the described circuit.
What is the effect of Rs and RL on the voltage gain of an amplifier?
it reduces the gain
What is common emitter amplifier with degeneration?
In electronics, a common-emitter amplifier is one of three basic single-stage bipolar-junction-transistor (BJT) amplifier topologies, typically used as a voltage amplifier. In this circuit the base terminal of the transistor serves as the input, the collector is the output, and the emitter is common to both, hence its name. An analogous circuit called the common source is constructed using field-effect transistors Common-emitter amplifiers generally have a very high gain which can vary widely from one transistor to the next, as it is a strong function of both temperature and bias current, making the actual gain unpredictable. Stability is another problem associated with such high gain circuits, due to any unintentional positive feedback that may be present. Other problems associated with the circuit are the low input dynamic range imposed by the small-signal limit and the high distortion resulting if this is exceeded. One common way of alleviating these issues is with the use of negative feedback, particularly with emitter degeneration. Emitter degeneration typically refers to the addition of a small resistor (or any impedance) between the emitter of the transistor and ground. The effect of this is to reduce the overall transconductance Gm = gm of the circuit by a factor of gmRE + 1, making the voltage gain depend more on the ratio of the resistors than the transistor's characteristics: The distortion and stability characteristics of the circuit are thus improved, but at the expense of a reduction in gain. Common-emitter circuits are used to amplify weak voltage signals, such as the faint radio signals detected by an antenna. When used in radio frequency circuits, it is common to replace the load resistor with a tuned circuit. This is done to limit the bandwidth to a narrow band centered around the intended operating frequency. More importantly it also allows the circuit to operate at higher frequencies as the tuned circuit can be used to resonate any inter-electrode and stray capacitances, which normally limit the frequency response. Common emitters are also commonly used as low noise amplifiers. At low frequencies and using a simplified Hybrid-Pi model, the following small signal characteristics can be derived. If the emitter degeneration resistor is not present, RE = 0 Ω. According to these formulas and in agreement with the previous discussion, when RE is increased the input resistance is increased and the gain is reduced. {| ! ! Definition ! Expression ! Current gain ! Voltage gain ! Input resistance ! Output resistance |} The bandwidth of the common emitter amplifier tends to be low, due to high capacitance resulting from the Miller effect. The base-collector capacitance is effectively multiplied by the factor 1 − Av, thus increasing the total input capacitance and lowering the overall bandwidth. The discussion of bandwidth parallels that in the article on the common source amplifier. A fix for this bandwidth problem is the cascode amplifier. == ==
What is effect on amplifier output if you increase input impedence?
Impedence is synonymous with resistense. Greater the I, lesser the outputNo.First, it's *resistance* and *impedance*.Now, if the amplifier is a current amplifier, the above makes sense. (higher Zin, less Iin for a constant Vin).But if it's a purely voltage amplifier, it only responds to the input voltage, so the impedance (so long as it's not affecting the source/driving device) will have no effect on a purely voltage-amplifying amplifier.
What is the effect in an input impedance of a common emitter amplifier if the bypass capacitor is removed?
The input impedance of a common emitter amplifier is hfe (or beta) times the sum of the emitter resistance, re = kT/qIc, plus the external impedance in series with the emitter. k - Boltzmann's constant, T - degrees Kevin, q - electron charge, Ic - collector current makes the intrinsic emitter resistance about 26 ohms at 1 ma. If the bypass capacitor impedance is much less than 26 ohms at the frequency of interest, then for a beta = 100 transistor operating at 1ma the input impedance is about 2600 ohms at low frequencies ie. 100 * (26 + 0). Say the external emitter resistance is 1K ohm and you remove the bypass cap. The total emitter resistance is now 26+1000 or 1026 ohms and the input impedance is now 100 * (26+1K ohms) or 102.6K ohms.
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.
What is the effect of bypass capacitor on frequency response?
Gain in a CE configuration of a BJT is collector resistance divided by emitter resistance, subject to the limit of hFe. The emitter bypass capacitor will have lower impedance at high frequency, so the gain will be higher at higher frequency, making this a high-pass amplifier.
Explain Ri and Ro effect the performance of bjt voltage amplifier?
aries.ucsd.edu/NAJMABADI/CLASS/ECE65/06-W/NOTES/BJT3.pdf
What effect does the bypass capacitor have on the output impedance of the amplifier?
The quantity of specific information included in the question is exceeded only bythe quantity of vital, relevant information that's never mentioned.Are you talking vacuum-tube or transistor amplifier ? What's the configuration of theamplifier, i.e., which terminal of the active device is 'common' to input and output ?And where is the bypass capacitor in the circuit ?I'll take a wild stab and assume that you have a common-emitter amplifier, with thecapacitor bypassing the bias resistor in the emitter branch. If that's the case, thenthe resistor is supposed to be there only to set the DC Q-point, but every effect itcould have on small-signal performance would be an effect that you don't want ...it would increase the output impedance, and any impedance common to input andoutput always reduces the gain.So one of the effects of the bypass capacitor is to reduce the output impedanceof the stage.(If Dingobot comes along now and flags this for gibberish, that'll be my first cluethat after all these years, I don't actually remember this stuff too well.)
