As per our previous article, we take a tutorial on common base transistor tutorial. Here we take the complete tutorial on common emitter transistor configuration. In common emitter type configurationemitter terminal is common between input and output circuit of transistor. Hence it names common emitter type transistor configuration.

In common emitter transistor configuration input is applied between base-emitter junction. Here we especially talk about common emitter configuration of bjt.

For common emitter configuration of NPN transistorwe take an emitter terminal is common between the input and output circuit of the transistor. You can see below fig 1 shows the common emitter connection of npn transistor.

For common emitter connection of the PNP transistorwe take an emitter terminal is common between the input and output circuit of the pnp transistor. You can see below fig 2 shows the common emitter connection of pnp transistor. For common emitter connection, the input current is base current Ib and the output current is collector current Ic.

Base amplification factor is generally the ratio of output current to the input current. So, the value of current amplification is greater than Characteristics of common emitter transistor represent the behavior of transistor for some input and output in a graphical way.

By the understanding characteristics, we can easily understand about the behavior of common emitter transistor. Here we look into the input and output characteristics of the transistor.

Input characteristics is a curve between base current Ib and base-emitter voltage Veb at a constant collector-emitter voltage Vcb. You can see the input characteristics in the figure. Base current is taken on the Y-axis and base-emitter voltage is taken on the X-axis. You can see the characteristics above.

The following points can be noted by input characteristics. For common base connection, the input resistance of a transistor is the ratio of base-emitter voltage to base current Ib.

Output characteristics is a graphical representation of output current and output voltage. For common emitter output characteristics, it curves between collector current Ic and collector-base voltage Vcb at a constant base current Ib.

You can see the output characteristics curves above. This curve we can draw by keeping base current constant in the circuit and take a reading of collector current Ic and collector-base voltage Vcb.

The following points we can take into consideration by this output characteristics. Output resistance is generally the ratio of output voltage to output current. Here for common emitter configuration output current is Ic and output voltage is Vcb. As we see above in points of output characteristics, the output resistance of a circuit is high. Common emitter transistor is first preferred in any application of transistor.

But here some advantages of this transistor because of that in practical life this transistor used in most applications. Common emitter CE transistor have some advantages over the common base and common collector connection. Common base CB Transistor gives high current gain but low voltage gain.In electronicsa common-emitter amplifier is one of three basic single-stage bipolar-junction-transistor BJT amplifier topologies, typically used as the 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 for example, it may be tied to ground reference or a power supply railhence its name.

The analogous FET circuit is the common-source amplifier, and the analogous tube circuit is the common-cathode amplifier. Common-emitter amplifiers give the amplifier an inverted output and can have a very high gain that may vary widely from one transistor to the next. The gain is a strong function of both temperature and bias current, and so the actual gain is somewhat 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; there is high distortion if this limit is exceeded and the transistor ceases to behave like its small-signal model.

common emitter

One common way of alleviating these issues is with emitter degeneration. This refers to the addition of a small resistor between the emitter and the common signal source e.

The distortion and stability characteristics of the circuit are thus improved at the expense of a reduction in gain. While this is often described as " negative feedback ", as it reduces gain, raises input impedance, and reduces distortion, it predates the invention of negative feedback and does not reduce output impedance or increase bandwidth, as true negative feedback would do.

At low frequencies and using a simplified hybrid-pi modelthe following small-signal characteristics can be derived. The bandwidth of the common-emitter amplifier tends to be low due to high capacitance resulting from the Miller effect. The Miller effect negatively affects the performance of the common source amplifier in the same way and has similar solutions. When an AC signal is applied to the transistor amplifier it causes the base voltage VB to fluctuate in value at the AC signal.

The positive half of the applied signal will cause an increase in the value of VB this turn will increase the base current IB and cause a corresponding increase in emitter current IE and collector current IC. As a result, the collector emitter voltage will be reduced because of the increase voltage drop across RL. It is also named common- emitter amplifier because the emitter of the transistor is common to both the input circuit and output circuit. The input signal is applied across the ground and the base circuit of the transistor.

The output signal appears across ground and the collector of the transistor. Since the emitter is connected to the ground, it is common to signals, input and output. The common- emitter circuit is the most widely used of junction, transistor amplifiers.

As compared with the common- base connection, it has higher input impedance and lower output impedance.

#273: Common Emitter Amplifier Design Tips \u0026 Shortcuts

A single power supply is easily used for biasing. In addition, higher voltage and power gains are usually obtained for common- emitter CE operation. Current gain in the common emitter circuit is obtained from the base and the collector circuit currents.Hello friends, I hope you all are doing great. In electronic engineering common emitter amplifier configuration is basic single-stage BJT amplifier technique it normally operate as voltage amplifier.

In this configuration base of transistor work as input collector as output terminal and emitter is common for both base and collector. In this circuit, arrangement emitter is connected with the ground so it also called grounded emitter configuration. So, friends, it is a detailed post about common emitter amplifier if you have a question ask in comments. Thanks for reading. I am a professional engineer and graduate from a reputed engineering university also have experience of working as an engineer in different famous industries.

I am also a technical content writer my hobby is to explore new things and share with the world. Through this platform, I am also sharing my professional and technical knowledge to engineering students. Your email address will not be published.

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Common Emitter Amplifier. Related Posts. Integrated Circuit Voltage Regulators September 23, How to Troubleshoot Amplifier Circuits April 3, Introduction to Differential Amplifier April 3, Introduction to Multistage Amplifiers April 3, Introduction to Sziklai Transistor Pair April 2, Common Base Amplifier April 2, Leave a Reply Cancel reply Your email address will not be published.As it consists of three basic terminals that are base, emitter and the collector but for the input and the output circuit connections it require minimum of four terminals.

In order to overcome this drawback a terminal among those three terminals made common so that it behaves in common for both input and output circuitry connections. When emitter is made common to both input and output then it becomes Common Emitter Transistor. This is one among the three configurations of these terminals. This configuration is the most widely preferred one because it has both current and the voltage gains which produces the high power gain value. When it operates in between cut-off and the region of saturation the transistor is said to be working as switch.

In order to make function as amplifier it must be operating in the region that is active. A transistor in which the emitter terminal is made common for both the input and the output circuit connections is known as common emitter configuration. In this type of configuration the input is applied at the terminal base and the considered output is to be collected across the terminal collector.

By keeping emitter terminal is common in both the cases of input as well as output. Let us considered a CE circuit is provided with the divider circuit of the voltage such that it is provided with the two resistors connected at the input side. In this type of configuration the base is considered to be the input terminal whereas the collector is for collecting the output.

Other than this there are various electronic components are to be included in this circuit. One is the resistor R1 that is the one to make the transistor to function in the forward biasing mode.

The R2 is responsible to make the biasing possible. There is the load resistor and the resistor that is connected at the emitter so that it controls the stability related to thermal issue. The resistors R1 and R2 connected across the terminal base as it is the input side. The load resistor is connected at the output side that is across the collector terminal. There are capacitors as well in the circuit. The capacitor C1 is at the input side and the capacitor C2 is connected across the emitter resistor.

There exists the inverse relation between the R1 resistor and the biasing. As R2 tends to increase the biasing tends to increase and vice-versa. Hence to the smaller or the weaker signals that are applied to the base gets amplified at the obtained output signals. Hence this is the reason it is known as CE amplifier. Further this ratio can be equated to the ratio of the resistance at the collector to the resistance value of the emitter.

Here the load resistance is the resistor connected across the collector. The ratio in between the output current to the applied input current gives the current gain. This is denoted as beta. In this way the values of the voltage gain and the current gain are calculated for this amplifier configuration.In common emitter configuration, base is the input terminal, collector is the output terminal and emitter is the common terminal for both input and output.

That means the base terminal and common emitter terminal are known as input terminals whereas collector terminal and common emitter terminal are known as output terminals. In common emitter configuration, the emitter terminal is grounded so the common emitter configuration is also known as grounded emitter configuration.

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Sometimes common emitter configuration is also referred to as CE configuration, common emitter amplifier, or CE amplifier. The common emitter CE configuration is the most widely used transistor configuration. The common emitter CE amplifiers are used when large current gain is needed. The input signal is applied between the base and emitter terminals while the output signal is taken between the collector and emitter terminals.

Thus, the emitter terminal of a transistor is common for both input and output and hence it is named as common emitter configuration. The supply voltage between base and emitter is denoted by V BE while the supply voltage between collector and emitter is denoted by V CE.

In common emitter CE configuration, input current or base current is denoted by I B and output current or collector current is denoted by I C. The common emitter amplifier has medium input and output impedance levels. So the current gain and voltage gain of the common emitter amplifier is medium. However, the power gain is high. To fully describe the behavior of a transistor with CE configuration, we need two set of characteristics — input characteristics and output characteristics. The input characteristics describe the relationship between input current or base current I B and input voltage or base-emitter voltage V BE.

First, draw a vertical line and a horizontal line. The vertical line represents y-axis and horizontal line represents x-axis. The input current or base current I B is taken along y-axis vertical line and the input voltage V BE is taken along x-axis horizontal line. To determine the input characteristics, the output voltage V CE is kept constant at zero volts and the input voltage V BE is increased from zero volts to different voltage levels.

Next, the output voltage V CE is increased from zero volts to certain voltage level 10 volts and the output voltage V CE is kept constant at 10 volts. After we kept the output voltage V CE constant at 10 volts, the input voltage V BE is increased from zero volts to different voltage levels.

Common Emitter Amplifier Circuit Working and Its Characteristics

This process is repeated for higher fixed values of output voltage V CE. When output voltage V CE is at zero volts and emitter-base junction is forward biased by input voltage V BEthe emitter-base junction acts like a normal p-n junction diode. So the input characteristics of the CE configuration is same as the characteristics of a normal pn junction diode. The cut in voltage of a silicon transistor is 0. In our case, it is a silicon transistor.

So from the above graph, we can see that after 0. In common emitter CE configuration, the input current I B is produced in the base region which is lightly doped and has small width.

So the base region produces only a small input current I B. On the other hand, in common base CB configuration, the input current I E is produced in the emitter region which is heavily doped and has large width.

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So the emitter region produces a large input current I E.Because transistors are able to control current in an analog fashion, they find use as amplifiers for analog signals. It is called the common-emitter configuration because ignoring the power supply battery both the signal source and the load share the emitter lead as a common connection point shown in the figure below.

This is not the only way in which a transistor may be used as an amplifier, as we will see in later sections of this chapter. Before, a small solar cell current saturated a transistor, illuminating a lamp. When there is just a little light shone on the solar cell, the lamp will glow dimly. Suppose that we were interested in using the solar cell as a light intensity instrument. We want to measure the intensity of incident light with the solar cell by using its output current to drive a meter movement.

It is possible to directly connect a meter movement to a solar cell for this purpose. The simplest light-exposure meters for photography work are designed like this.

Although this approach might work for moderate light intensity measurements, it would not work as well for low light intensity measurements.

Common Emitter Amplifier

Supposing that our need here is to measure very low-level light intensities, we are pressed to find another solution. It is prudent to point out that the additional power to move the meter needle comes from the battery on the far right of the circuit, not the solar cell itself.

common emitter

Because the transistor is a current-regulating device, and because meter movement indications are based on the current through the moving coil, meter indication in this circuit should depend only on the current from the solar cell, not on the amount of voltage provided by the battery.

This means the accuracy of the circuit will be independent of battery condition, a significant feature! All that is required of the battery is a certain minimum voltage and current output ability to drive the meter full-scale. Another way in which the common-emitter configuration may be used is to produce an output voltage derived from the input signal, rather than the specific output current.

With the solar cell darkened no currentthe transistor will be in cutoff mode and behave as an open switch between collector and emitter. This will produce a maximum voltage drop between collector and emitter for maximum V outputequal to the full voltage of the battery. At full power maximum light exposurethe solar cell will drive the transistor into saturation mode, making it behave like a closed switch between collector and emitter. The result will be a minimum voltage drop between collector and emitter, or almost zero output voltage.

In actuality, a saturated transistor can never achieve zero voltage drop between collector and emitter because of the two PN junctions through which collector current must travel. For light exposure levels somewhere between zero and maximum solar cell output, the transistor will be in its active mode, and the output voltage will be somewhere between zero and full battery voltage.

An important quality to note here about the common-emitter configuration is that the output voltage is inverted with respect to the input signal.

That is, the output voltage decreases as the input signal increases.

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For this reason, the common-emitter amplifier configuration is referred to as an inverting amplifier. A quick SPICE simulation figure below of the circuit in the figure below will verify our qualitative conclusions about this amplifier circuit. At the beginning of the simulation in the figure above where the current source solar cell is outputting zero current, the transistor is in cutoff mode and the full 15 volts from the battery is shown at the amplifier output between nodes 2 and 0.Definition : The configuration in which the emitter is connected between the collector and base is known as a common emitter configuration.

The input circuit is connected between emitter and base, and the output circuit is taken from the collector and emitter. Thus, the emitter is common to both the input and the output circuit, and hence the name is the common emitter configuration.

common emitter

The base current amplification factor is defined as the ratio of the output and input current in a common emitter configuration. In common emitter amplification, the output current is the collector current I C, and the input current is the base current I B. In other words, the ratio of change in collector current with respect to base current is known as the base amplification factor.

The Common-emitter Amplifier

We Known. In other words, the current gain in a common emitter configuration is very high, and because of this reason, the common emitter arrangement circuit is used in all the transistor applications.

If the base current is open i. The collector current is current to the emitter, and this current is abbreviated as I CEO that means collector- emitter current with the base open. The characteristic of the common emitter transistor circuit is shown in the figure below.

The base to emitter voltage varies by adjusting the potentiometer R 1. And the collector to emitter voltage varied by adjusting the potentiometer R 2.

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For the various setting, the current and voltage are taken from the milliammeters and voltmeter. On the basis of these readings, the input and output curve plotted on the curve. For drawing the input characteristic the reading of base currents is taken through the ammeter on emitter voltage V BE at constant collector-emitter current.

The curve for different value of collector-base current is shown in the figure below. The curve for common base configuration is similar to a forward diode characteristic.

Thus the input resistance of the CE configuration is comparatively higher that of CB configuration. The effect of CE does not cause large deviation on the curves, and hence the effect of a change in V CE on the input characteristic is ignored. The characteristic curve for the typical NPN transistor in CE configuration is shown in the figure below. In the active region, the collector current increases slightly as collector-emitter V CE current increases.

The slope of the curve is quite more than the output characteristic of CB configuration. The output resistance of the common base connection is more than that of CE connection. The collector-base junction of the transistor always in forward bias and work saturate. In the saturation region, the collector current becomes independent and free from the input current I B.

Output Resistance: The ratio of the variation in collector-emitter voltage to the collector-emitter current is known at collector currents at a constant base current I B is called output resistance r o.

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