This is a quick note to document how i analyzed a circuit that i found on a tutorial and verified a statement made on the tutorial about the minimum gain required to startup the oscillation. Use a 30pf capacitor in parallel with a variable capacitor. It can be shown that the colpitts family of oscillator never squegg. Connect cro at output terminals and observe wave form. Free running blocking oscillators simulation using spice. Combination of inductor and capacitors determine frequency of oscillator. They can be made from some of the active or passive devices like transistors, fets and opamps in combination with devices. Amplifiers and oscillators practical workbook covers those practical oriented circuits. Colpitts oscillator was invented by american scientist edwin colpitts in 1918. A complementary colpitts oscillator in cmos technology. A colpitts oscillator is the electrical dual of a hartley oscillator. This lab introduced the concept of feedback in combination with bipolar junction transistors. Repeat the above steps 2, 3 for different values of l1 and note down practical values of oscillations of colpitts oscillator.
Cmos colpitts oscillator either singleended or differential, see fig. Colpitts oscillator is an electronic oscillator which uses an inductor and capacitors to form an lc oscillator circuit. A low phasenoise kaband cmos voltagecontrolled oscillator is proposed in this paper. It is another type of sinusoidal lc oscillator and is basically a harmonic oscillator, which has a lot of applications.
Eltr 125 semiconductors 2, section 3 recommended schedule. Wien bridge oscillator, bjt question 52 day 3 topics. Sinewave feedback lc oscillators engineering projects. In the colpitts oscillator shown in fig 1, z1, and z2 are capacitors and z3 is aninductor. Calculate practically the frequency of oscillations by using the expression. It is type of feedback lc oscillator where feedback is supplied. Aeclab manual analog electronic circuitsaec laboratory. Because of high frequencies, small inductance can be used for the radio frequency of oscillation. Colpitts oscillator an overview sciencedirect topics. The colpitts oscillator uses a capacitive voltage divider network as its feedback source. May 26, 2016 the colpitts oscillator is a good circuit for this type of application. Connect the circuit diagram as shown in the figure. Frequency response, input and output impedance calculation 3. Rcphase shift, hartley, colpitts and crystal oscillators.
Lab work clapp oscillator using bjt transistor the. Describe the conditions of oscillation that the colpitts oscillator and hartley oscillator can operate in a proper way. The ett101 laboratory manuals volumes 1 and 2 provide a turnkey solution for the teacher and student alike. Colpitts, is one of a number of designs for lc oscillators, electronic oscillators that use a combination of inductors l and capacitors c to produce an oscillation at a certain frequency. Study the following oscillators and observe the effect of variation of c on oscillator frequency.
The feedback needed for oscillation is taken from a voltage divider made of two capacitors, whereas in the hartley oscillator the feedback is taken from a. One difference in practical implementation between the colpitts oscillator and the hartley oscillator is that, in the case of the hartley, l 1 and l 2 can be, and often are, implemented as a single coil winding with a center tap. Colpitts,1is one of a number of designs for lc oscillators, electronic oscillatorsthat use a combination of inductorsl and capacitorsc to produce an oscillation at a certain frequency. The colpitts configuration can be recognized by its use of a tapped capacitor divider c 1 and c 2 in figure 1. Colpitts oscillator project gutenberg selfpublishing. Build the colpitts oscillator shown using either breadboard proto board or strip board, then test the oscillator s operation using a multi meter and oscilloscope. It will operate from a 9v battery, or a dc power supply up to 12v. May 06, 2020 build the colpitts oscillator shown using either breadboard proto board or strip board, then test the oscillator s operation using a multi meter and oscilloscope. E ece, iisem aec lab manual colpitts oscillator aim.
The way this idea works is that instead of canceling the input to reduce gain, the output is combined in phase with the input to create oscillations. To determine the frequency of oscillations of a given colpitts oscillator. Communication circuit lab manual experiment 5 colpitts oscillator eng. In previous lessons and experiments, you learned that amplifier gains of. Colpitts oscillator gju electrical and communication. Amplitude of oscillation in colpitts oscillator using describing function method is egual to v2i c r l c2c1. Each chapter includes background information which relates the experiment content to. Introduction oscillators are circuits that produce specific, periodic waveforms such as square, triangular, sawtooth, and sinusoidal. This electronics video tutorial provides a basic introduction into the colpitts crystal oscillator circuit. Colpitts, 1 is one of a number of designs for lc oscillators, electronic oscillators that use a combination of inductors l and capacitors c to produce an oscillation at a certain frequency.
Phaseshift and resonant oscillator circuits questions. The frequency of the oscillator can be from around 500 khz to 2 mhz depending on the values chosen for c 1, c 2 and l 1. The phase shifter oscillator the phaseshifter consists of a negative gain amplifier k with a third order rc ladder network in the feedback. To study the basic operations of colpitts oscillator b. Figure 2 shows crystal oscillator using colpitts circuit using bjt. Sine wave oscillators are used as references or test waveforms by many circuits. Niknejad university of california, berkeley eecs 142 lecture 22 p. Each chapter includes background information which relates the experiment content to realworld applications. R1 and r2 are biasing resistors and rfc is the radio frequency choke, which provides the isolation between ac and dc operation.
In lab you will have a chance to consider both a sinusoidal oscillator the socalled colpitts oscillator, named after its inventor and a relaxationtype oscillator. The distinguishing feature of the colpitts oscillator is that the feedback for the active device is taken from a voltage divider. Colpitts oscillator theory sakshat amrita virtual lab. The resistors r and r2 and re provide the necessary dc bias to thetransistor. A lesson learned from lab testing a colpitts oscillator. Can replace tuning capacitor with a varactor circuit to implement electronic tuning. Frequency response, input and output impedance calculation 2. Crystal operates above series resonance and acts like a very high q inductor. The circuit will oscillate at the frequency for which the phase shift of the rc onetwork is 180. The idea of this project was to build and test a colpitts voltage controlled oscillator vco frequency modulated fm radio and conduct circuit analysis on the vco.
Colpitts crystal oscillator schematic shows some practical values and one way to accomplish bias. The manuals are specially written to guide students through handson experiments and help them grasp the fundamental concepts of telecommunications. Half wave, full wave and bridge rectifier circuits 68 12. The oscillator in your transmitter will use a colpitts lc oscillator. He specifically looked at a colpitts oscillator with automatic gain control. Lee, ala ee 314 real ground ac ground ac ground common base amp biasing like ce but. The goal of this lab was to first create a circuit that had known poles, and then introduce feedback and view the effect on the frequency of the poles.
An oscillator is a type of feedback amplifier in which part of the output is fed back. This oscillator circuit can produce a sine wave output in excess of 10 vpp at an approximate frequency set by the value chosen for l 1. Analog electronics laboratory manual 10esl37 dept of ece gcem page v list of experiments sl no title page no 1 rectifiers 1 2 clippers and clampers 7 3 zener diode 20 4 bjt amplifiers 23 5 bjt darlington emitter follower 27 6 hartley and colpitts oscillator 31 7 crystal oscillator 38 8 class b push pull amplifier 41. The frequency of oscillation can be calculated in the same way as any parallel resonant. The distinguishing feature of the colpitts oscillator is that the feedback for the active device is taken from a voltage divider made. The colpitts oscillator is a particularly good circuit for producing fairly low distortion sine wave signals in the rf range, 30khz to 30mhz. Hartley oscillator hartley oscillator circuit and working.
Positive feedback amplifiers oscillators lc and crystal. In many cases, the op amp is thought of as an ideal op amp. This means that it will produce a nearly constant frequency output. The circuit diagram of a hartley oscillator is shown in the below figure.
The presence of this c3 extra capacitance compared to colpitts will make the clapp oscillator preferable over colpitts, when there is a need to vary the frequency as is the case with variable frequency. Try to design a hartley oscillator as shown in figure 1. Communication circuit lab manual experiment 5 colpitts oscillator. Firstorder, smallsignal analysis dutton improved large signal version t. Analog electronic circuits lab manual ssit, tumkur. Bjt multivibrator circuit, astable question 51 day 2 topics. A manuallycontrolled variable resistor or capacitor can be an. The cmos vco core adopts a new complementary colpitts structure in a 0. This topology is exactly the same as the circuit analyzed by huang except the location of the ground node has been moved to the source. Transistor based collpits oscillator simulation in multisim. Conduct an experiment on series voltage regulator using zener diode and. High frequency oscillators are generally lc oscillator, for example.
Tunedinput and tunedoutput oscillator tunedoutput tunedinput feedback coupling ci rf output c 2 c 1 l 1 2 c co c l 2 1 2 0 2 1 1 l c f s. Circuit used to study the operation of colpitts oscillator is as shown in figure 2. Analog electronic circuits lab ssit 27 colpitts oscillator. Analog electronics laboratory manual 10esl37 gopalan colleges. This colpitts oscillator produces a sine wave output in excess of 12vpp at an approximate frequency set by the values chosen for l1, c2 and c3.
Remove all metal jewellery since rings, wrist watches or bands, necklaces, etc. This type of oscillator uses a split capacitor to obtain positive feedback. Do not make circuit changes without turning off the power. Study of operation of colpitts oscillator equipments needed. Virtual lab at amrita uses stateoftheart computer simulation technology to create real world environments and problem handling capabilities is required to bridge the gap between institutions or industries that retain the physical laboratory and distantly placed economically challenged educational institutions in areas such as physics, chemistry and biotechnology.
Laboratory manual for electronics via waveform analysis. Its operating frequency is fairly stable compared to other oscillator configurations hartley, armstrong, etc. Here crystal is placed in place of inductor l of colpitts tuned circuit. The way this idea works is that instead of canceling the input to reduce gain, the. Always wear tight shirt lab coat, pants and shoes inside workshops. Colpitts oscillator tutorial and colpitts design electronics tutorials. A study of phase noise in colpitts and lctank cmos oscillators. The two capacitors, the emitter terminal of the transistor is effectively. It is another type of sinusoidal lc oscillator and is basically a harmonic oscillator, which has a. A colpitts oscillator, invented in 1918 by american engineer edwin h. Tuned oscillator is a circuit that generates a radio frequency output by using lc tuned resonant circuit. Electronic circuit lab simulation lab any six hardware lab any two s.
Lab work clapp oscillator using bjt transistor the single transistor classic colpitts oscillator with the component values is given in figure 2. To design a colpitts oscillator and to observe its output waveform. Now for a more challenging oscillator colpitts oscillator analysis and design. Colpitts family if we remove the explicit ground connection on the oscillator, we have the template for a generic oscillator. Some of my recent personal work has been focused on detecting cars in my cabins driveway by using a loop of wire that experience an inductance change when a car passes over it. Quick look at a colpitts oscillator math encounters blog. It is the weekend and time to build my personal circuits. Compare the values of frequency of oscillations both procedure. Ee3 lab 2 using oscillators to generate fm signals. Ec2257 electronic circuits ii and simulation lab cycle i 1. A colpitts oscillator is a discrete lc oscillator that uses a pair of tapped capacitors and an inductor to produce regenerative feedback. It is type of feedback lc oscillator where feedback is supplied capacitively. An npn transistor connected in a common emitter configuration works as the active device in amplifier stage. There are many different types of oscillators that can be created with op amps, one of which is the colpitts oscillator.
1339 1350 626 707 1264 1322 1367 1446 571 1205 1459 670 255 279 730 220 461 1161 1006 1184 616 1046 655 302 946 786 810 812 1408 996 1368 280