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What if base current is zero in a transistor used as an amplifier with common emitter configuration?
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∙ 12y ago
output current is zero
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∙ 12y ago
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What is the function of emitter bypass capacitor in common emitter amplifier?
The emitter bypass capacitor in a common emitter amplifier will have less resistance as the frequency increases. Since gain in this configuration is collector resistance divided by emitter resistance (within limits of hFe), the gain will thus increase for higher frequencies, making this into a high pass filter.
What is an emitter follower?
This is a particular transistor amplifier configuration. In general, the input signal is applied to the base, the collector is connected to a supply voltage, and the output is taken between the emitter and power supply common. One of the characteristics of the emitter follower is the output voltage "follows" the input, but the output is reduced by the Vbe voltage (the voltage drop between base and emitter, approximately 0.7 V for a silicon bipolar transistor).
Why Common Emitter Configuration is most commonly used in amplifier circuits?
the common emitter configuration is most widely used in amplifer circuits because of its high voltage,current & power gain.the common emitter configuration is most widely used in amplifer circuits because of its high voltage,current & power gain.
Why emitter current flows away from base in NPN transistor?
arrows are shown for conventional current, not electron current.
How do you design a bjt amplifier with gain 10?
To design a bjt amplifier with gain 10, consider that gain in a class A common emitter configuration is collector resistance divided by emitter resistance. So, pick the two resistors so that their ratio is ten. Bias the base so that the collector is at the center of the operating voltage range, along with the transistor being at the center of its linear region. Of course, you need to consider impedance and operating current, so you need to choose carefully. Also, the beta (hFe) of the transistor must be substantially more than ten for this to work reliably. Often, this voltage gain stage is followed by a class C common collector emitter follower to give you current gain as well.
What configuration commonly employed in bipolar transistor amplifier?
Common Emitter - Class A Amplifier.
How transister work as amplifier?
A transistor works as am amplifier by virtue of the fact that you can control the current in one path with a smaller current in another path. In a typical class A (common emitter) configuration, a certain current from base to emitter will create a corresponding current from collector to emitter. Increasing or decreasing the base-emitter current will cause a corresponding increase or decrease in the collector-emitter current, by a ratio that is defined as hFe, or beta-gain. Of course, this means that you have to properly bias the transistor, and understand the nature of hFe. You can operate a transistor in cutoff mode or saturated mode if you exceed the hFe limits. Within the limits, a properly biased transistor exhibits a (generally) linear operation.
Why base in grounded in common emitter transistor as amplifier?
With a common emitter amplifier it's the emitter that is usually grounded.
What is the difference between a transistor used as a switch and an amplifier?
A transistor used as a switch is operated in saturated mode, where the ratio of base-emitter current over collector-emitter current is far more than hFe, or beta gain. The transistor is either fully on or fully off in this mode. A transistor used as an amplifier is operated in linear mode, where the ratio of base-emitter current over collector-emitter current is equal to or less than hFe, or beta gain. The transistor is partially on in this mode, and is operating as a current controlled current sink.
How does a transistor amplify in a common emitter configuration?
The base is excited by a very low current. That turns the transistor on so that a higher amount of current flow comes out.
Transistor as an amplifier common emitter configuration explanation using kirchhof's law?
Kirchoff's current law states that the current in every point in a series circuit is the same. In the case of a transistor in common emitter configuration, you can take advantage of that fact and state that the collector current is equal to the emitter current. The truth is somewhat different, because the gain of the transistor is not infinity, so the base current must be added to the emitter current. With a reasonably high gain, however, you can ignore the base current. Consider that the emitter voltage is related to the base voltage by the forward drop of the base-emitter junction, about 0.7 volts, and the collector and emitter currents are the same. Now look at the collector and emitter resistors. If the currents are the same, and the voltage across the emitter resistor is known, then you know the voltage across the collector resistor as well. This is an application of both Kirchoff's and Ohm's laws. The gain, then, of this amplifer is collector resistance divided by emitter resistance. It is an inverting amplier in this configuration. In some configurations, the emitter resistor is zero ohms. This does not mean the gain is infinity - it now means that the gain is limited by the gain of the transistor, which it is anyway - the emitter resistor is used to stabilize the gain and reduce dependency on individual transistor gains, which do vary.
How transistor produce 180 degree phase shift?
In the common emitter configuration, a class A amplifier, an increase in base voltage (the input) leads to an increase in base-emitter current which leads to a proportionately larger increase in base collector current. That pulls the collector towards the emitter, which decreases the collector voltage. Since the collector is the output, this configuration is an inverting amplifier.
Why is npn transistor called emmitor follower?
In an NPN transistor an emiter follower refers to an amplifier topology. The emiter follower configuration is when the emitter of a N-Type Bipolar Junction Transistor (BJT) is connected to the common point on a circuit (typically ground). This is not always the case, however, because many amplifier configuration exist.
What is the function of emitter bypass capacitor in common emitter amplifier?
The emitter bypass capacitor in a common emitter amplifier will have less resistance as the frequency increases. Since gain in this configuration is collector resistance divided by emitter resistance (within limits of hFe), the gain will thus increase for higher frequencies, making this into a high pass filter.
Why common emitter configuration is mostly used for transistor as switch?
because in ce configuration value of input voltage requried to make the transistor on is very less value of the output voltage or output current
In a common emitter transistor the primary purpose of a resistor connected to the emitter is to?
The emitter resistor in a common emitter configuration provides negative feedback to the transistor, reducing both its voltage gain and distortion.
Which transistor configuration has the highest input impedance?
Common Emitter Configuration has maximum impedance.
