BJT Common Base Characteristics
Bjt common base - input characteristics.
- Initially set rheostat R h1 = 1 Ω and rheostat R h2 = 1 Ω
- Set the Collector-Base Voltage(V CB ) to 1 V by adjusting the rheostat R h2
- Base Emitter Voltage(V BE ) is varied by adjusting the rheostat R h1 .
- Note the reading of emitter current(I E )in m Ampere.
- Click on 'Plot' to plot the I-V characteristics of Common-Base configuration. A graph is drawn with VBE along X-axis and IE along Y-axis.
- Click on 'Clear' button to take another sets of readings
- Now set the Collector-Emitter Voltage(V CB ) to 2 V, 3 V, 4 V
BJT Common Base - Output Characteristics
- Set the Emitter current(I E )1 mA by adjusting the rheostat R h1
- Vary the Collector-Base Voltage(V CB )is varied by adjusting the rheostat R h2 .
- Note the reading of Collector current(I C ).
- Click on 'Plot' to plot the I-V characteristics of Common-Base configuration. A graph is drawn with V CBalong X-axis and I C along Y-axis.
- Now set the Emitter Current(I E ) to 2 mA
Input and output characteristics of common base configuration
Since transistor is a three terminal device, therefore, it can be connected in a circuit in three different ways:
- Common-base configuration
- Common-emitter configuration
- Common-collector configuration
Definition – In common base configuration , base terminal of transistor is common between the input and output circuits.
The graphs showing the relationship between different currents and voltages of a transistor are known as the characteristics of the transistor . The characteristics of a transistor are of two types:
- Input Characteristics.
- Output Characteristics.
- 1.1.1 Early effect or base width modulation
- 1.2.1 Active region
- 1.2.2 Saturation region
- 1.2.3 Cut off region
- 1.3 What is the output characteristics of common base configuration?
- 1.4 What is common base characteristics?
- 1.5 What is a common base configuration?
The graph between voltages and currents when the base terminal of a transistor is common to input and output circuit are known as common base transistor characteristics of a transistor .
The circuit diagram to study the input and output characteristics of common base configuration of a transistor is shown in the figure.
Characteristics of a transistor in common base configuration are of two types:
- input characteristics common base configuration.
- output characteristics common base configuration .
Input Characteristics of common base configuration
The graph showing the variation of emitter current ( I E ) with the variation of emitter-base voltage ( V EB ) when a collector-base voltage ( V CB ) is kept constant is known as input characteristics of a transistor.
It can be written as V EB = f ( V CB , I E )
A set of input characteristics are shown in the figure.
A transistor in fact consists of two diodes in series i.e. a PN junction diode in contact with another and np junction diode. So when the emitter-base junction is forward biased, the variation of I E with V EB is similar to the forward characteristics of a PN junction diode .
From the input characteristics, it is clear that there is a cut in or off set of threshold voltage below which there is no emitter current or the emitter current is very small. The value of threshold voltage = 0.1 V for Ge transistor and threshold voltage = 0.5 V for Si transistor.
Early effect or base width modulation
When a transistor is not biased, the width of the base region is W as shown in the figure. When the emitter-base junction is forward biased and the collector-base junction is Reverse Biased, emitter current I E increases with an increase in V EB at a fixed V CB .
However, when V CB increasing, the width of the depletion layer at the collector-base junction increases. As a result of this, the effective width of the base region decreases.. if the width of the depletion layer at the collector junction penetrating the base region is W’, then the effective width of the base region is equal to W – W’.
This change of the effective width of the base region by the reverse Bias Voltage of collector junction is known as early effect or base width modulation. Due to this effect, the gradient of the holes concentration in the base region increases with the increase in a reverse bias V CB for a given value of V EB .
Thus, Emitter current I E increases with the increase in V CB .
The Dynamic input resistance = Δ V CB / Δ I E .
Since a small change in V EB causes a large change in I E so the Dynamic input resistance of junction Je is very small. At a certain reverse bias of collector junction, the depletion layer at the collector junction covers the whole base region so the effective width of the base reduced to zero.
As a result of this, the potential barrier at the emitter junction decreases and hence large emitter current flows. This phenomenon is known as punch through . The value of the collector voltage at which punch through takes place is called punch-through voltage.
Output Characteristics of common base configuration
The variation of collector current I C with the collector-base voltage (V CB ) at constant emitter current ( I E ) is called output characteristics of the transistor in the common base configuration. It can be written as I c = F (V CB , I c ).
It is clear that the output characteristics of a transistor in the common base configuration are divided into three regions :
| 1. | |
| 2. | |
| 3. |
Active region
In this region, the emitter-base junction J E is forward biased and collector-base junction J C is reversed biased. If I E = 0, then the transistor behaves as a PN junction diode formed by base and collector part of the transistor. In this case, the collector current I C is equal to the reverse saturation current I CO . The magnitude of I CO is constant and independent of V CB.
Now let us suppose, small emitter current I E flows. Since only a few holes entering the base region from the emitter Recombine with the electrons in the base region, so most of the emitter current reaches the collector. Then the collector current, I C = I CO – α I E
Where α Is the fraction of total emitter current which represents the holes that have traveled from the emitter to the collector through the base.
The collector current I C depends only on the value of I E and independent of V CB.
Saturation region
In this region, both the junction i.e emitter-base junction ( J C ) and collected base junction ( J e ) is forward biased. Thus, for pnp transistor, the saturation region of the output characteristics lies to the left of V CB = 0 and above I E =0 .
In fact, V CB Is slightly positive. As the collector junction is forward biased, so the collector current I C increases exponentially with V CB just like in PN junction diode. That is why I C increases with a small increase in V CB in this region. The holes from the Collector (P region) cross the junction to enter the base region under the condition of forwarding bias.
Thus, hole current flows from the collector region to the base region. This hole current flows just opposite to the hole current flows from the collector region to the base region. Hence, the net hole current fin the transistor decreases. If the forward bias is high, then the hole current from the collector I C becomes positive.
Cut off region
In this region, both the emitter-base junction and collector-base junction are reverse biased. This region lies I E =0 and to the right side of V CB =0 .
What is the output characteristics of common base configuration?
What is common base characteristics?
What is a common base configuration.
In common base configuration , base terminal of transistor is common between the input and output circuits.
- Electron Devices
- _Rectifiers
- _Transistors
- _Special semiconductor devices
- _Power and display devices
- Digital Electronics
- Data Science
- _Python Libraries
Common Base configuration, input and output characteristics
common base configuration:.
| Common Base configuration |
Two terminals are needed for input and two terminals are needed for output, so one terminal is taken as common for both input and output. Based on the terminal which is taken as common there are three types of configurations. They are
- Common base configuration
- Common emitter configuration
- Common collector configuration
In common base configuration base terminal taken as common for both input and output. Input is applied between emitter and base terminal and output is taken between collector and base terminal.
Common emitter configuration and Common collector configuration are widely used and common base configuration is the least used.
Circuit diagram of Common Base NPN and PNP transistor:
In the Common base circuit for NPN and PNP the input is given between emitter and base terminals and output is taken from collector and base terminals. The input voltage is denoted as V BE and the output voltage is denoted as V CE . In all the configuration the base emitter junction is always forward biased and the collector base junction is reverse biased.
| Common Base configuration of PNP transistor |
| Common Base configuration of NPN transistor |
In the common base configuration of NPN circuit emitter is N type base is of P type and collector is of N type. The emitter base terminals are forward biased so the majority charge carriers in the emitter that is the electrons gets repelled by the negative applied voltage and in the same way the majority charge carriers in the base that is the holes gets repelled by the positive applied voltage.
When free electrons from emitter move to the base the free electrons and the free holes combine with each other but since the base is very thin only some free electrons gets combined with the holes and the majority of the electrons are attracted towards the collector because of the positive terminal voltage connected to the collector. Thus the current flow through the output terminal.
Thus the emitter current is the sum of the base current and the collector current.
I E = I B +I C
In common base configuration, the input impedance is low and the output impedance is high and the overall power gain is low when compared with other configuration.
Input characteristics:
| Input characteristics of Common Base configuration |
Input characteristics are the relationship between the input current and input voltage with constant output voltage. In common base configuration input current is emitter current I E and the input voltage is base emitter voltage VBE. The curve is plotted between I E and V BE keeping V CB as constant.
The V BE is increased keeping V CB constant, initially at zero and the input current I E is noted, similarly the V CB value is increased and kept constant and V BE is increased and the input current I E is noted.
Input side is forward biased so the input resistance is small so for a small increase in V BE there is rapid increase in the emitter current I E . As the output voltage V CB is increased the width of the depletion layer between emitter base decreases and the cut in voltage is reduced so the curve drifts to the left side.
Output characteristics:
| Output characteristics of common base configuration |
Output characteristics are the relationship between output current I C and output voltage V CB keeping input current I E constant. When the input current I E is zero it is in cut off region. In saturation region both emitter base junction and collector base junction are forward biased.
In active region I E is gradually increased and kept constant and output voltage V CB is increased further and the output current I C almost remains constant. So in active region curve is almost flat. Output voltage causes only a very little change in output current.
You may like these posts
Post a comment, social plugin.
- Data Science 55
- Deep Learning 1
- Digital Electronics 19
- Electronic devices 49
- Exploratory data analysis(EDA) 5
- Feature Engineering 6
- Machine Learning 14
- Minimization techniques 19
- Power and display devices 6
- Python for data science 40
- Python Libraries for data science 8
- Rectifiers 4
- Special semiconductor devices 14
- Transistors 15
Popular Posts
Common emitter configuration, input and output characteristics, common collector configuration, input and output characteristics, menu footer widget.
- Privacy policy
COMMENTS
This web page provides the list of experiments and apparatus required for Electrical Engineering Materials & Semiconductor Devices Lab (EC-317-F) in III semester. It also gives the brief theory, circuit diagram, procedure, observation table, graph, result, discussion and quiz for each experiment.
The DC characteristics of BJTs can be presented in a variety of ways. The most useful and the one which contains the most information is the output characteristic, IC versus VCB and IC versus VCE shown in Fig. 3. Figure 3. Typical I-V characteristics of BJT for (a) common base and (b) common emitter configuration. 4.
Learn about the history, construction, symbols, biasing and configurations of bipolar junction transistors (BJTs) in this PDF document. BJTs are three terminal devices that can amplify weak signals and are widely used in electronic systems.
Exp 8: Transistor Characteristics PHY 321, 2022F C B E + V 0 A I E V CE V V V BE A I B 100k 10k Figure 2: Circuit for characterizing a bipolar junction transistor. Note the polarity of the DC voltage source, which is shown appropriate for a PNP transistor. The polarity would be opposite when working with an NPN transistor. 4 Procedure 1.
Learn about the key features, modes, and parameters of bipolar junction transistors (BJTs), a type of transistor device formed by pn junctions. See diagrams, equations, and examples of BJT characteristics, such as current gain, output conductance, and breakdown voltage.
hermometer design discussed in Chapter 1.Specifications: The electronic thermometer is to operate. over a temperature range of 0 to 100 °F.Design Approach: The output-diode voltage developed in the diode thermometer in Figure 1.48 is to be applied to the base-emitter junction of an npn bipolar trans-istor to enhan.
The most important characteristic of the BJT is the plot of the emitter current, I E, versus the base-emitter voltage,V BE, for various values of the collector-base voltage, V CB. IE = ϕ(VBE,VCB) for constant VCB I E = ϕ (V B E, V C B) f o r c o n s t a n t V C B. Figure 4: Input Characteristics Circuit.
Experiment. BJT Common Base - Input Characteristics; Initially set rheostat R h1 = 1 Ω and rheostat R h2 = 1 Ω ; Set the Collector-Base Voltage(V CB) to 1 V by adjusting the rheostat R h2; Base Emitter Voltage(V BE) is varied by adjusting the rheostat R h1. Note the reading of emitter current(I E)in m Ampere.
6-i. Experiment 6. Transistors as amplifiers and switches. Our final topic of the term is an introduction to the transistor as a discrete circuit element. Since an integrated circuit is constructed primarily from dozens to even millions of transistors formed from a single, thin silicon crystal, it might be interesting and instructive to spend a ...
The three configurations of BJT amplifiers, i.e., common emitter (CE), common collector (CC), and common base (CB). CE configuration is also referred to as the "inverter" configuration, and CC and CB are referred to as the emitter (or voltage) follower and current buffer, respectively. BJT is always biased in the forward-active region (FAR ...
EXPERIMENT 11: NPN BJT COMMON EMITTER CHARACTERISTICS AIM: To study input and output characteristics of a NPN Bipolar Junction Transistor (BJT) in Common-emitter configuration. APPARATUS: BJT (BC-547B), Bread board, resistor (1KΩ, 100KΩ), connecting wires, Ammeters (0‐10mA, 0‐100μ A), DC power supply (0‐30V) and
of curves is organized by base current since the diode-like characteristics of the current vs. base-emitter voltage would make the voltages of each curve very similar (and highly susceptible to process variations). Figure 3 shows the opposite type of curve, with a plot of collector current as the base-emitter voltage is swept. The
Base Current • Base current has two components - hole diffusion current from base to emitter - electron recombination in base • The base current also has a diode-like expression for current, but is a fraction of the collector current. It is given in terms of a parameter called the common-emitter current gain, β, and the collector ...
The purpose of this experiment are to familiarize the student with • the response of the three Bipolar Junction Transistor (BJT) amplifier configurations. ... There are three basic BJT amplifier configurations that are generally identified as: common- emitter, common-base, and common-collector (sometimes called the emitter-follower). Each of
Experiment No. 2 CE, CB & CC CONFIGURATIONS Aim: To study the input and output characteristics of a transistor in Common Emitter configuration. Apparatus Required: S.No. Name Quantity 1 Transistor BC 107 1(One) No. 2 Resistors (1K , 100K ) 1(One) No. Each 3 Bread board 1(One) No. 4 Dual DC Regulated Power supply (0 - 30 V) 1(One) No.
Learn how to design and analyze BJT amplifiers with common-emitter and emitter-follower configurations. Understand the bias network, the signal path, the large-signal and small-signal models, and the voltage transfer characteristic.
Learn how to measure and plot the input and output characteristics of a BJT in common base configuration using virtual labs. Adjust the rheostats and click on 'Plot' to see the graphs of VBE, IE, VCB and IC.
Introduction. Transistors are the active component in various devices like amplifiers and oscillators. They are called active devices since transistors are capable of amplifying (or making larger) signals. The proper-ties of transistors will be studied in this module so basically the focus here is understanding how transis-tors work.
Learn about the input and output characteristics of a transistor in common base configuration, a circuit where the base terminal is common to both input and output. Find out how the emitter current, collector current and collector-base voltage vary with each other and what are the regions of operation.
The configuration used in the context of this laboratory experiments is common emitter. (see figure 2) A common emitter configuration provides both voltage and current gain, where the input signal is between the base and emitter and the output signal is between the emitter and collector. In this configuration, the emitter is connected to both the
Learn the structure, operation and characteristics of bipolar junction transistor (BJT) in common emitter configuration. See the equations, graphs and applications of BJT as a switch, amplifier and oscillator.
To study input and output characteristics of a NPN Bipolar Junction Transistor (BJT) in Common-emitter configuration. Introduction Of Theory:-The transistor is a two junction, three terminal semiconductor device which has three regions namely the emitter region, the base region, and the collector region. There are two types of transistors.
Learn how to draw the circuit diagram and explain the working of common base configuration of NPN and PNP transistors. See the input and output characteristics, the current and voltage relations, and the regions of operation.