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Actually the current gain is equal to Beta+1, not Beta. The current from/into the emitter is the sum of the current into/from the collector and base. Of course this assumes linear operation.
For a proof: Ie + Ib + Ic = 0
Ic = Beta * Ib
Ie + Ib + Beta * Ib = 0
Ie + (Beta + 1) * Ib = 0
Ie = -(Beta + 1) * Ib
Wiki User
∙ 11y ago
Wiki User
∙ 11y agoFor high current gain when voltage gain is not required. Non-inverting.
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Define current gain of a common emitter configuration?
The voltage gain of a common emitter transitor amplifier is (inverted) collector resistor divided by emitter resistor, unless this would exceed hfe or the transistor is operating in non-linear mode.
The emmiter current of an n-p-n transistor is equal to?
The sum of (base current) plus (collector current).
Why more current amplification in common emitter?
A bipolar transistor can be used in different configurations in linear electronic design. Most well known is the common emitter CE configuration with a base current as input signal resulting in a collector signal multiplied by the current gain factor. The second configuration is known as the emitter follower or common collector configuration. Here the input signal is in the form of a voltage between the base and the common connection. The output signal is found in the form of a voltage at the emitter with a relative low output impedance. The voltage swing at the input is almost as large at the output where the input impedance equals the product of the current gain factor and the emitter resistance. The third configuration is known as common base CB. Here the input current at the emitter almost equals the output current at the collector. The current gain is nearly equal to 1.
What is meant by biasing in a single stage ce amplifier?
Biasing in a single stage common-emitter amplifier means to place the base-emitter current at a point where the collector-emitter current is in the middle of the transistor's linear range.First, you pick the target range and output impedance of the amplifier, picking the collector and emitter resistors. The gain of the stage is collector resistance divided by emitter resistance, limited by available hFe. You want to try to pick a resistor pair that will place the collector voltage in the center of the desired range, while keeping the desired operating current where you want it.Then, you pick the base resistor divider pair such that the base voltage is the forward bias drop of the base-emitter above (NPN) or below (PNP) the emitter voltage. You find that emitter voltage by considering the collector voltage, along with the operating current and the collector and emitter resistors. (Its straightforward Ohm's law, considering that the collector-emitter forms the third resistor in the divider chain.) You have to consider hFe in this calculation, as well as realizing that the two base resistors will form the input impedance of the stage. (Well, actually, base-emitter current is included in the input impedance calculation, but that is usually a small contribution if the hFe is high enough.)Then you need to consider the power dissipation in the stage, and make sure that the transistor can handle that, and that hFe will not drift unacceptably under temperature. (Stable designs are such that the hFe is far greater than the ratio of collector resistance over emitter resistance, so that your limits are based on ratio, and not on hFe. Problematic designs are when the desired gain is greater than hFe, such as when the emitter resistance is zero - this makes gain equal to hFe, and introduces the possibility of thermal runaway.)
Why CB amplifier preferred for high frequency than CE amplifier?
1)in cc configuration we use to get the low output impedence where as in ce we use to get the high output impedence. 2)in cc amplifier we use to have the voltage gain equal to unity where as in ce amplifier we use to have the high voltage gain. 3)in cc amplifier there is high power gai which is used for impedence matching where as in ce amplifier due to the high voltage gain the impedence matching is less impossible.
What are the characteristics of a CB amplifier?
it is a mode of amplifier connection where the base part of the transistor is made common to both input and output.the circuit diagram is as shown below. the transiator gain(represented by the greek letter beta-B) is usually evaluated by the formula B=output current divided by input current. as we know that when the transistor is connected in common base mode the input pert will be emitter and the output part will be collector and we know that the collector current is quiet less than emitter current. as per the formula gain will be less than one. practically we consider emitter current as equal to collector current and hence B approaches 1 in case of common base mode amplifiers.as the gain is very less it is very less used as amplifiers. generally they use common emitter mode for amplification as this mode optimum amount of amplification.
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.
Define current gain of a common emitter configuration?
The voltage gain of a common emitter transitor amplifier is (inverted) collector resistor divided by emitter resistor, unless this would exceed hfe or the transistor is operating in non-linear mode.
Why is the base current in a transistor so much less than the collector current?
as the base current is very small compared to the emitter current,the collector current is nearly equal to the emitter current..
Why the base current in the transistor is so much less than the collector?
as the base current is very small compared to the emitter current,the collector current is nearly equal to the emitter current..
The emmiter current of an n-p-n transistor is equal to?
The sum of (base current) plus (collector current).
How does emitter current is equal to base current and collector current?
Consider that current flow "enters" at the emitter and "exits" at the collector and base. Now, IE = IB + IC. Alternately, current "enters" at the collector and the base, and "exits" at the emitter. Now, IE = IB + IC
How a transistor transfers resistance?
The input current of transistor is approximately equal to output current .Suppose in common base configuration the emmiter current is approximately equal to collector current if neglect the very small value of bae current.Even though the input resistance is not equal to output resistance,the currents are same ,so we can reliase that the transistor transfers resistance to get same currents at both ends.
Why is the base of transistor made very thin?
Base of transistor is made thin just to get Collector current equal to Emitter current.
Why more current amplification in common emitter?
A bipolar transistor can be used in different configurations in linear electronic design. Most well known is the common emitter CE configuration with a base current as input signal resulting in a collector signal multiplied by the current gain factor. The second configuration is known as the emitter follower or common collector configuration. Here the input signal is in the form of a voltage between the base and the common connection. The output signal is found in the form of a voltage at the emitter with a relative low output impedance. The voltage swing at the input is almost as large at the output where the input impedance equals the product of the current gain factor and the emitter resistance. The third configuration is known as common base CB. Here the input current at the emitter almost equals the output current at the collector. The current gain is nearly equal to 1.
What is the Frequency response of common emitter amplifier?
The voltage gain is a measure of the amplified output available at the collector terminal divided by the voltage measured on the base. This if you have 10 mV applied to the base and voltage of 1 volt at the collector the voltage gain is 100ANSWERThe maximum voltage gain of a common emitter amplifier is dependant on the transistor itself. Some have only a very small voltage gain such as in Radio Frequency Power transistors. These are almost all used as common emitter circuits for bipolar transistors or common source for FETs.. On the other hand some darlington transistors can have common emitter gains of hundreds of thousands. If the stage has an unbypassed emitter resistor, the voltage gain is equal to Rload/RE, (Rload is the parallel value of the resistance from collector to the supply and the resistance of the load).If the emitter resistance is bypassed, the value of resistance to be used for RE is the internal Re which is equal to 25mV/Ie
What is meant by biasing in a single stage ce amplifier?
Biasing in a single stage common-emitter amplifier means to place the base-emitter current at a point where the collector-emitter current is in the middle of the transistor's linear range.First, you pick the target range and output impedance of the amplifier, picking the collector and emitter resistors. The gain of the stage is collector resistance divided by emitter resistance, limited by available hFe. You want to try to pick a resistor pair that will place the collector voltage in the center of the desired range, while keeping the desired operating current where you want it.Then, you pick the base resistor divider pair such that the base voltage is the forward bias drop of the base-emitter above (NPN) or below (PNP) the emitter voltage. You find that emitter voltage by considering the collector voltage, along with the operating current and the collector and emitter resistors. (Its straightforward Ohm's law, considering that the collector-emitter forms the third resistor in the divider chain.) You have to consider hFe in this calculation, as well as realizing that the two base resistors will form the input impedance of the stage. (Well, actually, base-emitter current is included in the input impedance calculation, but that is usually a small contribution if the hFe is high enough.)Then you need to consider the power dissipation in the stage, and make sure that the transistor can handle that, and that hFe will not drift unacceptably under temperature. (Stable designs are such that the hFe is far greater than the ratio of collector resistance over emitter resistance, so that your limits are based on ratio, and not on hFe. Problematic designs are when the desired gain is greater than hFe, such as when the emitter resistance is zero - this makes gain equal to hFe, and introduces the possibility of thermal runaway.)
