The emitter follower or common collector circuit is widely used in amplifier configuration of bipolar junction transistors bjts with gain of unity or less. The dc analysis of npn and pnp configurations is quite different in the sense that the currents will have opposite directions and the voltages. Unilateral amplifier is the one in which rin may depend on rl and rout. Rc is called the collector resistor and re the emitter resistor. To build and test a similar circuit, go to experiment 6 in your lab manual laboratory. It is the function of base current ib and vbe baseemitter voltages at constant collector emitter voltage vce input characteristics curve can be obtained by keeping the output voltage vce constant and varying the input voltage vbe and then record the value. Solution tutorial 2 bjts, transistor bias circuits, bjt. Thus the collector terminal is common to both the input and output circuits. Bjts, transistor bias circuits, bjt amplifiers fets and fets amplifiers. The emitter follower common collector amplifier assumptions. Special application resettable power tb9 operating voltage. Operating point collector current depends on two circuit parameters. Im trying to build a common base colpitts oscillator for a project in my university.
Transistors characteristics are graphs of the various currents ibis current into the base, ie is current out of the emitter, and icis current into collector and voltages. Common collector amplifier basic electronics tutorials. The commoncollector amplifier input and output resistance. Lessons in electric circuits volume iii chapter 4 bipolar. Figure 2 is the schematic for a simple npn commoncollector emitterfollower digital ampli fier. We can even use the miller theorem to calculate the gain of this circuit for finite opamp gain g. Basically, the bipolar junction transistor consists of two backto. The common emitter configuration has a current gain approximately equal to the. The differential pair responds only to the difference mode signals and rejects commonmode signals. In activity 3, you will build a circuit known as the emitter follower.
It is called a common emitter amplifier since the emitter is common to both the input circuti and the output circuit. The emitter follower configuration is mostly used as a voltage buffer. H1lin this circuit r c is at ac ground at both ends. In this post we learn how to use a transistor emitter follower configuration in practical electronic circuits, we study this through a few different example application circuits. The current gain of a commoncollector amplifier is equal to. Common collector configuration in the common collector or grounded collector configuration, the collector is now common through the supply. We are interested in the bias currents and voltages. The voltage signal applied at the input will be duplicated at the output. Common base colpitts oscillator all about circuits. For dc, c e is an open circuit and r e can participate in the definition of the dc load line and qpoint. Bjt modeling and r model small signal analysis e transistor.
Permission is granted to copy, distribute andor modify this document under the terms of the gnu free documentation license, version 1. It is the line on the output characteristics of a transistor circuit which gives the values of i c and v ce corresponding to zero signal or dc conditions. Describe and analyze the operation of common collector amplifiers describe and analyze the operation of common base amplifiers describe and analyze the operation of multistage amplifiers discuss the differential amplifier and its operation troubleshoot amplifier circuits key terms visit the website study aids, multisim, and lt spice files for. 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. Common emitter as the emitter is at signal ground because of c3. What is common collector connection or cc configuration. Working and applications of common collector amplifier. The auxiliary trouble input is an open collector circuit which can be used to monitor external devices for trouble conditions.
Common collector amplifier or emitter follower circuit and. The analysis or design of any electronic amplifier therefore has two. You will find a practical design and analysis of a classa, common emitter amplifier in this post. Common collector amplifier common collector amplifier has a large current and power gain, excellent stability and frequency response. Emitter follower or common collector amplifier circuit. In the common collector configuration the load resistance is situated in series with the emitter so its current is equal to that. 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. There are additionally three capacitors but they do not play a role in the basic transistor amplifier design which mainly involves setting dc voltages.
An emitter follower is one of the standard transistor configurations which is also referred to as common collector. Highfrequency nonlinearity analysis of commonemitter and. The circuit can be explained by viewing the transistor as being under the control of negative feedback. The commoncollector amplifier is a well known circuit see figure 1. Describe and analyze the operation of commoncollector amplifiers describe and analyze the operation of commonbase amplifiers describe and analyze the operation of multistage amplifiers discuss the differential amplifier and its operation troubleshoot amplifier circuits key terms visit the website study aids, multisim, and lt spice files for. I know this is the basic layout of a common collector colpitts oscillator but what do i need to add to the circuit to make it functional. The output impedance of this circuit is equal to the value of the emitter resistor, this circuit is used for impedance matching. In electronics, a common collector amplifier is one of three basic singlestage bipolar junction. Commonemitter commonbase commoncollector input impedance z in moderate r r r1 2. The analogous fet circuit is the common source amplifier, and the analogous tube circuit is the common cathode amplifier.
The transistor is biased with a common supply such that the base emitter junction is forward biased and the collector base junction is reversed biased, i. The voltage at the common emitter point e will now be 0. This article discusses the working of the common emitter amplifier circuit and its applications. Commoncollector configuration of a transistor youtube.
Basecollector junction the depletion region at this junction is usually divided between base and collector, since they are comparably doped. The emitter follower, also known as the common collector cc ampli er, is shown in figure 5a with its biasing circuit in place, with two dc voltage source v cc and v ee. The commoncollector circuit is suited as a driver stage for connecting with a low impedance load. Introduction any increase in ac voltage, current, or power is the result of a transfer of energy from the applied dc supplies. Input characteristics curve of common emitter configuration. It is called a common emitter amplifier since the emitter is common to both the. The load resistance of the common collector transistor. Find materials for this course in the pages linked along the left. Common emitter amplifier working principle and its. In the common emitter or grounded emitter configuration, the input signal is applied between the base, while the output is taken from between the collector and the. Input characteristics of common collector circuit is a curve between input current here base current ib and input voltage here basecollector voltage vcb at constant emittercollector voltage vec. The eb junction is forwardbiased by v ee and cb junction is reversebiased by v cc.
The configuration in which the collector is common between emitter and base is known as cc configuration. All structured data from the file and property namespaces is available under the creative commons cc0 license. Bipolar junction transistor circuits voltage and power amplifier circuits common emitter amplifier the circuit shown on figure 1 is called the common emitter amplifier circuit. Microelectronics circuit analysis and design, 3 rd edition. Transistor configurations common emitter, base and. The voltage gain of the amplifier is less than but close to unity. The common collector amplifier is considered a voltagebuffer since the voltage gain is unity. Department of eecs university of california, berkeley eecs 105fall 2003, lecture 17 lecture 17. Help with simulating common collector amplifier in pspice.
To save this circuit, go to the file menu, select save file, and enter the desired location and file name. The input signal is connected directly to the base, while the output is taken from the emitter load as shown. The ac smallsignal equivalent circuit is shown in figure 5b. Common collector configuration of transistor detailed. The input signal is injected into the base collector circuit and output signal is taken out from the emitter collector circuit. Make sure that you are comfortable with this representation, and. Transistor equivalent circuits and models learning objectives general dc equivalent circuit ac equivalent circuit equivalent circuit of a cb amplifier effect of source resistance r s on voltage gain equivalent circuit of a ce amplifier equivalent circuit of a cc amplifier smallsignal lowfrequency model or representation. Lecture notes microelectronic devices and circuits. Read the tutorial designing a commoncollector amplifier for help completing this prelab. Ive tried various times to build the actual circuit, but the oscilloscope isnt reading anything from my circuit. This w3cunspecified circuit diagram was created with the. Ce, b common base cb, and c common collector cc courtesy.
Ive been looking around the forum and i cant seem to find any information about colpitts oscillator in a common collector configuration. Although the circuit above shows an enhancement nmos, these configurations are valid for all jfets and mosfets discussed. Common collector configuration inputoutput characteristics relation between. Not as obvious, but still legitimate, is the other name for this configuration the emitterfollower.
Sometimes common collector configuration is also referred to as emitter follower, voltage follower, common collector amplifier. The input signal v i is applied to the base and the output v o is off the collector. The bipolartransistor common emitter and differentialpair. For the common collector configuration, the model defined for the common emitter configuration of is normally applied rather than defining a model for the common collector configuration. Common emitter configuration commonly used in lownoise amplifiers. In a true common collector circuit the value of rc is zero ohms. The common collector amplifier can be thought of as a current amplifier. The commoncollector amplifier is also known as an emitterfollower.
It should be apparent that the load resistor in the common collector amplifier circuit receives both the base and collector currents, being placed in series with the emitter. The object is to solve for the smallsignal voltage gain, input resistance, and output resistance. This is the correct answer for the closed loop gain as we shall later see. Also, keep in mind that the circuit capacitors serve as coupling or bypass, depending on.
In common collector configuration, the collector terminal is grounded so the common collector configuration is also known as grounded collector configuration. The output voltage on a commoncollector amplifier will be in phase with the input voltage, making the commoncollector a noninverting amplifier circuit. Output impedance z out moderate rc moderate rc low 1 2 s e 0 r r r r r 1. The collector voltages will be v o1 v cc and v o2 vcc. Emitter follower or common collector amplifier circuit this tutorial will help you to build and simulate a more complex circuit. The equations derived in this article are symbolic, as is the derivation of any other formula in this website. This configuration is also known as emitter follower configuration because the emitter voltage follows the base voltage. What links here related changes upload file special pages permanent link page. The commoncollector amplifier can be thought of as a current amplifier.
Ce fixed bias circuit as shown in the figure, it is the common emitter fixedbias configuration. The input current i i is not the base current and the i o is the collector current. 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. Bipolar junction transistor circuits voltage and power.
It has a voltage gain that is always less than 1 unity. For smallsignal analysis, v cc is replaced with ground. Design a commoncollector amplifier using a 2n3904 npn bjt to meet the following specifications hand in all calculations. Ece 255, bjt basic configurations purdue engineering. Common emitter amplifiers are also used in radio frequency transceiver circuits. Dc solution a replace the capacitors with open circuits. The miller theorem and the frequency response of the common. It has a high input impedance and a low output impedance. Common emitter amplifier with re and emitter degeneration. Calculate the approximate amount of ac voltage output by this commoncollector amplifier circuit. It is mostly used as a buffer due to its high input resistance, small output resistance and unity gain.
At high collector voltage the collector current depends on the base current only. For the commoncollector configuration, the model defined for the commonemitter configuration of is normally applied rather than defining a model for the commoncollector configuration. Study aids, multisim, and lt spice files for this chapter are. The input signal is injected into the basecollector circuit and output signal is taken out from the emittercollector circuit. Ive been failing at this for somewhat over a month now. Common base circuit 359 common collector circuit 359 quiz 361 23 the field effect transistor 365 principle of the jfet 365. Common collector means that the collector is a common point for both input and output signals ie. The capacitor cb is used to couple the input signal to the input port of the ampli. Class a bjt amplifiers this worksheet and all related files. Since the emitter lead of a transistor is the one handling the most current. Commoncollector configuration of a transistor topics covered. Lessons in electric circuits volume iii chapter 4 bipolar junction transistors introduction the transistor as a switch meter check of a transistor active mode operation the commonemitter amplifier the commoncollector amplifier the commonbase amplifier the cascode amplifier biasing techniques biasing calculations o base bias o collector.
Descriptiondiagram showing the common collector type of. Why is the base current in a transistor so much less than the collector current. Explain the purpose of a thin, lightly doped base region. Not surprisingly, this leads to the name commoncollector for this circuit. This type of configuration is commonly known as a voltage follower or emitter follower circuit. An application of the miller theorem input impedance of the inverting amplifier if opamp has zero y in. Free download principles of transistor circuits introduction to the design of amplifiers, receivers and digital circuits ebook. This type of bipolar transistor configuration is a non inverting circuit in that the signal voltages of. The bipolar junction transistor is used in two broad areas of electronics.
In common collector transistor configuration, we use collector terminal as common for both input and output signals. Basic structure of the circuit used to realize singlestage, discrete circuit bjt amplifier. Fields of application for the commoncollector circuit. Phy 351651 laboratory 6 the bipolar junction transistor bjt. The commoncollector amplifier is considered a voltagebuffer since the voltage gain is unity. The common collector amplifier is one of the three basic bjt amplifier topologies. In activity 2, using these characteristic curves, you will then design, build and operate an important circuit known as the commonemitter amplifier. Phy351651 the bipolar junction transistor bjt lab 6 configuration known as the commonemitter configuration. 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 other circuit, but provide a lower impedance to the following stages. The biasing resistor network made up of resistor r1and r2 and the voltage supply vcc. It can be connected to the trouble bus of a peripheral, such as a power supply, which is compatible with open collector circuits. Common collector colpitts oscillator all about circuits.
This can be seen by considering the behavior of the bypass capacitor c e. This is also called the common drain cd and is analogous to the common collector a. In cc configuration, the input circuit is connected between emitter and base and the output is taken from the collector and emitter. The commoncollector circuit is a basic transistor amplifier with current gain. Electrical characteristics mc34063ab, mc34063ac, mc34063eb, mc34063ec 623 docid5257 rev 12 4 electrical characteristics refer to the test circuits, v cc 5 v, t a t low to t high, unless otherwise specified. 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. The circuit is also referred to as the grounded collector ampli fier. All amateur radiorelated projects, tips, tricks, and tools. Introduction the rapid growth of portable wireless communication systems has led to a demand for lowpower, highperformance, and highly integrated rf circuits. There are three di erent con gurations in which the bjt can function common base, common emitter, and common collector.
193 161 1666 11 665 495 1002 223 148 1172 1275 1516 574 1583 228 474 927 566 1203 1147 385 1116 797 1219 1311 1117 92 156 364 66 8 1442 365 365 1357 202