A common collector amplifier is one of three basic singlestage bipolarjunctiontransistor bjt amplifier topologies, typically used as a voltage buffer. Input characteristics of common collector circuit is a curve between input current here base current ib and input voltage here base collector voltage vcb at constant emitter collector voltage vec. The analogous fet circuit is the commonsource amplifier, and the analogous tube circuit is the commoncathode amplifier. An common emitter amplifier circuit has a load resistance, r l of 1. The source v bb is applied to the input circuit in addition to the signal. While collector is common between base and emitter terminals. Difference between common base common emitter and common collector.
The circuit can be explained by viewing the transistor as being under the control of negative feedback. Bjt common collector amplifier analog electronics course. The voltage gain of an emitter follower is just a little less than one since the emitter voltage is constrained at the diode drop of about 0. Design the circuit shown in figures 1 and 2 by calculating the values of r 1, r 2, r 3 and r 4. Apr 27, 2020 a common collector circuit analysis has a voltage gain of 1, no phase shift between input and output, high input impedance, and low output impedance. In this circuit, the base of the transistor serves as an input, emitter as the output and the collector is grounded that is, common for both emitter and base. This circuit provides same current gain as common emitter circuit.
It has a high input impedance and a low output impedance. Common collector connection or cc configuration circuit globe. The object is to solve for the smallsignal voltage gain, input resistance, and output resistance. Because the base to emitter voltage in a bipolar transistor is essentially constant it is determined by the effective base to emitter diode potential, roughly 0. Introduction there are three types of configurations in which transistor operation is carried out namely cb,ce,cc.
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 rail, hence its name. With proper biasing, we can use it as a current amplifierca, voltage amplifierva, transconductance anplifiertca as well as transresistance amplifiertra. The commoncollector amplifier is a well known circuit see figure 1. Help with simulating common collector amplifier in pspice. Current amplifier factor y the current amplification factor is defined as the ratio of the output current to the input current. Since the emitter lead of a transistor is the one handling the most current, it would be reasonable to presume that this amplifier will have a very large current gain. Common collector amplifier or the emitter follower. Thus, the commonemitter amplifier is called an inverting amplifier circuit. Jul 08, 2018 a common collector amplifier is one of three basic singlestage bipolarjunctiontransistor bjt amplifier topologies, typically used as a voltage buffer. Npn common collector amplifier georgia state university. Multisim simulation of common collector amplifier youtube. Fields of application for the commoncollector circuit.
Because of its high z i, low z o, and unity gain, the cc circuit is normally used as a buffer amplifier, placed between a high impedance signal source and a low impedance load. Common collector means that the collector is a common point for both input and output signals ie. This means that the emitter follower circuit provides an ideal buffer stage, and as a result it is used in many circuits where there is a need not to load a circuit like an oscillator or. The commoncollector amplifier bipolar junction transistors.
Although the common collector amplifier is not very good at being a voltage amplifier, because as we have seen, its small signal voltage gain is approximately equal to one a v. In this circuit the base terminal of the transistor serves as the input, the emitter is the output, and the collector is common to both and connected. It is used in the frequency generation circuit to increase the strength of the input signal. Common emitter as an amplifier is a configuration of the basic bipolar junction transistor bjt. So lets get started with common collector amplifier.
The collector is to be treated common for both input and the output sides or sometimes considered to be grounded. Larger values will still work, but with reduced output voltage swing. For the common emitter amplifier circuit, the input is applied to the base, and the output is taken from the collector. In this circuit the base terminal of the transistor serves as the input, the emitter is the output, and the collector is common to both signal input between base and common collector. Common collector amplifier or emitter follower circuit for that we set the quiescent point need to be set with the circuitry external to the transistor, the values of resistors rc and rb, and the dc voltage sources, vcc and vbb, have chosen accordingly. What is common collector connection or cc configuration. Such type of arrangement is known as a common collector because the collector is linked with the ground. To fully describe the behavior of a transistor with cc configuration, we need two set of characteristics input characteristics and output characteristics. A common collector amplifier, also called an emitter follower, has the collector in both the input circuit and the output circuit. Operating point collector current depends on two circuit parameters. The input signal is given to the emitter through capacitor coupling. In our previous articles we have learned the other two transistor configurations, namely the common base and the common emitter. In common collector amplifier, input is applied to bc junction and output is taken from ec terminal, here collector terminal is common for both input and output. Mar 30, 2019 the common collector amplifier is one of the three basic bjt amplifier topologies.
It is mostly used as a buffer due to its high input resistance, small output resistance and unity gain. The transistor bjt, fet is a major component in an amplifier system. It is also known as an emitter follower and is used as a voltage buffer. In electronics, a common collector amplifier also known as an emitter follower is one of three basic singlestage bipolar junction transistor bjt amplifier topologies, typically used as a voltage buffer. As we see in the previous article, there is basically three type of transistors connections. In this article, we will discuss the commoncollector amplifier circuit. The output voltage on a commoncollector amplifier will be in phase with the input voltage, making the commoncollector a noninverting amplifier circuit. Difference between common base common emitter and common. A commoncollector amplifier, also called an emitter follower, has the collector in both the input circuit and the output circuit. In this article, we present the last topology of amplifiers for bipolar transistors known as the common base amplifier cba.
The circuit uses voltage divider bias to derive the transistor base voltage v b from the supply. An amplifier circuitry which is designed by considering the collector terminal to be common for the input and the output sides is defined as common collector amplifier. The collector is common to both the input and output circuit and hence the name common collector connection or common collector configuration. Often the collector of the previous stage will be at approximately the mid rail voltage, and this means that it can be directly coupled to the buffer stage. Common collector configuration physics and radioelectronics. Table 62 compares z i, z o, and a v, for difference between common base common emitter and common collector circuits. The commoncollector circuit is a basic transistor amplifier with current gain. In this circuit the base terminal of the transistor serves as the input, the emitter is the output. A closer look at the common emitter amplifier and emitter. The commoncollector amplifier instrumentationtools. Thus the collector terminal is common to both the input and output circuits. The common collector amplifier is another type of bipolar junction transistor, bjt configuration where the input signal is applied to the base terminal and the output signal taken from the emitter terminal.
Tmodel as opposed to the hybrid typically provides the. The current gain of a commoncollector amplifier is equal to. The common collector junction transistor amplifier is commonly called an emitter follower. Working and applications of common collector amplifier. It is used to increase the speed of fans, motors, and. A bjt common collector amplifier is a circuit in which the collector and the base of the bjt share a common input supply, hence the name common collector. It is used in microphones, radio, and music players. Common collector amplifier basic electronics tutorials. Common emitter amplifier working, characteristics and. Common collector amplifier or emitter follower circuit and. The common emitter transistor amplifier is the only configuration that gives an inversion, 180, between the input and output signals.
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. Aug 07, 2019 common emitter amplifier configuration is widely used due to its advantage of moderate current and voltage gain. The basic purpose of the amplifier is to amplify the signals and that improvises the strength of the signal. Common emitter connection, common base connection, and common collector. Dc coupled emitter follower, common collector circuit. Apr 01, 2020 while collector is common between base and emitter terminals. The common collector amplifier is one of the three basic bjt amplifier topologies. What are the application of common emitter amplifier. Transistor common collector homemade circuit projects.
Common collector amplifier the engineering knowledge. Common collector amplifier, design, characteristics and. Here we cover topics common collector configuration of the transistor circuits, characteristics, applications, disadvantage, why it is called emitterfollower circuit. Application of a common collector amplifier circuit. Unlike the common emitter amplifier, the output voltage of the common collector amplifier is in phase with the input voltage. The current gain of a commonemitter transistor amplifier with the load connected in series with the collector is equal to the voltage gain of a commonemitter transistor amplifier is approximately given here. The commoncollector circuit is suited as a driver stage for connecting with a low impedance load.
The simplest way of connecting an emitter follower is to directly couple the input as shown below. It turns out that for commoncollector amplifiers, the. The voltage gain of the amplifier is less than but close to unity. The common collector amplifier is a well known circuit see figure 1. In the common collector circuit analysis cc shown in fig. Dc solution a replace the capacitors with open circuits.
Its voltage gain is close to unity one and, therefore, any increment in the input voltage i. Why is common collector transistor called emitter follower. The v bb battery provides the forward bias voltage to the emitterbase junction of the transistor. Transistor emitter follower, common collector amplifier. The commoncollector amplifier is used for coupling circuits with small driving capabilities with heavy loads. With proper biasing, we can use it as a current amplifier ca, voltage amplifier va, transconductance anplifiertca as well as transresistance amplifier tra. The power gain of the common collector amplifier is medium. A common collector amplifier is one of three basic singlestage bipolar junction transistor bjt amplifier configurations. Voltage, current and power gains of common collector amplifier. Its function is not voltage gain but current or power gain and impedance matching.
Apr 27, 2020 difference between common base common emitter and common collector. In figure 1 below, the electric diagram of a cba is presented, no particular bias circuit or decoupling capacitors are shown here. Bjt amplifiers 6 chapter outline 61 amplifier operation 62 transistor ac models 63 the commonemitter amplifier 64 the commoncollector amplifier 65 the commonbase amplifier 66 multistage amplifiers 67 the differential amplifier 68 troubleshooting device application chapter objectives describe amplifier operation discuss transistor models. The main difference between the two will be where the output is taken. Ce mode is the universal mode of operation for a bjt. The common terminal for both circuits is the emitter. Fields of application for the common collector circuit. Transistor common emitter amplifier electronics notes. Common emitter amplifier the common emitter npn amplifier circuit is shown in the figure below. Common emitter amplifier circuit working and characteristics.
An amplifier circuit is generally designed with one or more transistors is called a transistor amplifier. The following image shows a typical common base amplifier circuit with voltage divider bias configuration. Oct 05, 2019 an amplifier circuitry which is designed by considering the collector terminal to be common for the input and the output sides is defined as common collector amplifier. Base of the bjt is the common terminal and is at ac ground due to the capacitor. In this article, we will discuss the common collector amplifier circuit. In todays post, we will have a detailed look at its circuit and some other related parameters. Common collector configuration of transistor detailed. Common base amplifier configuration, circuit, characteristics.
It is normally used as a buffer, because it has a high input. Figure 1a gives the basic circuit of a common collector amplifier, popularly called emitter follower. The reason for this can be seen from the fact that as the input voltage rises, so the current increases through the base circuit. The commoncollector amplifier is also known as an emitterfollower. Having in mind the expressions and characteristics of the voltage gain, the input and output resistances, lets consider the following circuit with a transistor gain of. The common collector circuit is suited as a driver stage for connecting with a low impedance load. Common collector circuit analysis input and output impedance. As already discussed, the ce circuit has high voltage gain, medium input impedance, high output impedance, and a 180 phase shift from input to output.
In figure 1 below, the electric diagram of a cba is presented, no particular bias circuit or decoupling capacitors are shown here fig 1. The commoncollector amplifier can be thought of as a current amplifier. The analogous fet circuit is the common source amplifier, and the analogous tube circuit is the common cathode amplifier. The common collector circuit is a basic transistor amplifier with current gain. Oct 03, 2019 common emitter as an amplifier is a configuration of the basic bipolar junction transistor bjt. Jul 29, 2019 in common collector amplifier, input is applied to bc junction and output is taken from ec terminal, here collector terminal is common for both input and output.
It is also known as voltage follower and it is moderately used amplifier circuit because it has a good current gain but the voltage gain is unity. At high collector voltage the collector current depends on the base current only. Common emitter amplifier its working characteristics. Application of a common collector amplifier circuit answers. The magnitude of the forward bias voltage should be such that it should keep the emitterbase junction always in. Thus in a commonemitter amplifier, a positive going signal is converted into a negative going output signal i. It is highly known for its feature of producing higher values of the gain in current. In a true common collector circuit the value of rc is zero ohms. Calculate the maximum collector current ic flowing through the load resistor when the transistor is switched fully on saturation, assume vce 0. The common emitter amplifier and emitter follower will be demonstrated using the same amplifier circuit. It should be apparent that the load resistor in the commoncollector amplifier circuit receives both the base and collector currents, being placed in series with the emitter.