Amplifier Definition and 560 Threads

An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the power of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is a circuit that has a power gain greater than one.An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device. Amplification is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. Amplifiers can be categorized in different ways. One is by the frequency of the electronic signal being amplified. For example, audio amplifiers amplify signals in the audio (sound) range of less than 20 kHz, RF amplifiers amplify frequencies in the radio frequency range between 20 kHz and 300 GHz, and servo amplifiers and instrumentation amplifiers may work with very low frequencies down to direct current. Amplifiers can also be categorized by their physical placement in the signal chain; a preamplifier may precede other signal processing stages, for example. The first practical electrical device which could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Today most amplifiers use transistors.

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  1. M

    Differential limiting amplifier

    HI i know that the circuit attached to this thread is a differential limiting amplifier , and the collector of Q2 acts as a current source , but other than that , i can't get my mind around it ! P1 is the input , P5 is the output , and Vcc is +12 connected to the 27 R . could someone...
  2. J

    Designing an AGC Amplifier Circuit for a Dynamic Range of 1Hz to 1MHz

    Hello All, I'm working on designing a simple circuit that takes a square wave clock input and converts it to a sine wave using a Johnson Counter, an R2R ladder and an output filter capacitor (see the below link for reference)...
  3. A

    Input and output of an operational amplifier

    Homework Statement The question is about the concept of the operational amplifier in electronics. For an ideal op. amp., it is said that the input impedance is infiinite and the current allowed by the op.amp. through its input terminal zero or in the case of a practical op.amp., it is...
  4. B

    Common base amplifier current gain

    Hi folks - I'm trying to follow along in a textbook the derivation of the common-base current gain equation, and I'm having a bit of trouble. The common base current gain is supposed to be approximately \alpha, where \alpha = \frac{\beta}{\beta+1}. Doing a nodal analysis with the signal applied...
  5. C

    Amplifier negitive feedback capacitor and resistor in paralell

    ok so if we have an amplifier with direct negative feedback we have a voltage follower if we put a resistor between that inverting input pin and ground, we can do these things: if we put another resistor between the output and the inverting input we can adjust the gain if, instead, we...
  6. L

    Need help with a 12 watt Audio amplifier

    I have recently built a 12 watt amplifier spec'd by G. Randy Sloan. The problem I am having is many fold. 1.) I am not an EE and learning as I am going 2.) The amp WILL carry a signal but so far I have only been able to use it as a passive circuit. 3.)The output leads don't provide an...
  7. K

    An amplifier that works in reverse?

    I am making a circuit of a car toy. Actually, i have already done its first step. The next step i want to make a one which is able to reverse and i think i will need an amplifier which can work in both biases (foward and reverse). So do exist amplifiers that can work in reverse as well as in...
  8. N

    Is a transistor a switch or an amplifier

    After doing some research, I am still confused is a transistor a switch or an amplifier. If it can be used as a switch how do I find the part that will work with the gate voltage that I give it. mouser.com wasn't really helping me in finding the right part.
  9. D

    Engineering Calculating Output Voltage of an Amplifier with RC Coupling Network

    Hi I am struggling to answer this question: The input coupling circuit of the amplifier shown in the figure consist of an RC network, with R = 1 kW and C = 5mF fed by a sinusoidal voltage source of r.m.s. amplitude of 200 mV. Assuming that the input impedance of the amplifier is, at all...
  10. S

    Operation amplifier audio equalizer

    Homework Statement I am to construct a circuit which can provide variable gain for the bass, midrange, and treble frequencies of an input. One of the stipulations is that I should use as few elements as possible. Homework Equations n/a The Attempt at a Solution Right now the only...
  11. X

    Multistage BJT Amplifier Design

    Homework Statement 1. Vcc = 15V 2. 10 Vp-p symmetrical output swing 3. Av >= 1000V/V 4. Rin >=10k 5. Rout <=500 6. flow <= 100Hz 7. fhigh >=1MHz 8. Power Consumption <= 500mW 9. Rload=2k Homework Equations Many :) The Attempt at a Solution We...
  12. B

    Building power amplifier. Need some help with schematics

    Hi everyone, I'm new to this forum. I'm working on a senior project where we are using ultrasonic transducers at very high frequencies. Problem is we only have some weaker 25V power supplies to drive the transducers. To fix this problem we were going to purchase a power amplifier but due to...
  13. S

    How Does the Offset Current Affect dVo/dt in an LM353 Op-Amp Circuit?

    Homework Statement Look up the offset current for the LM353 op-amp and predict the time rate of change of the output for the circuit below after the switch opens. (Find dVo/dt) Homework Equations offset current = 50 pA i+ = i-, ideally v+ = v-, ideallyThe Attempt at a Solution I really don't...
  14. M

    Servo amplifier to control dc motor

    hi, sorry my English isn't perfect but please try to understand : my teacher gave me a project in which i have to use a small dc motor,op amp,and a "servo amplifier" to control the rotation of the shaft of the motor, so can you tell me what is the servo amplifier? and how to use it to control...
  15. C

    Differential Amplifier Common Mode Problem

    There are a couple of things I don't understand about the DA in general and when we use it in the common mode in particular (same input ac voltage to both input terminals). I am using Electronic Circuit and Theory by Louis Nashelsky and Robert Boylstad (p.591 for DA). When we set the...
  16. K

    Semiconductor Optical Amplifier Static and Dynamic Design

    Hie. I would like to know anyone who knows or have idea on design static and dynamic model for Semiconductor Optical Amplifier? Currently my lecturer ask me to design using Optisystem software which I quit blur on designing this models. Anyone who knows and help me please. Thanks in advanced..
  17. T

    Operational Amplifier Dependencies

    Hi Does anyone know of any dependencies for op amps? for example: does it have a temperature dependence?
  18. T

    Summing amplifier results dont agree with theory

    i had to do a study using a summing amplifier to see if the results i got agreed with theory, the answers i got was something like 9.62, the answer i should of got was 10, now this doesn't seem that far away, BUT the errors didnt agree at all, they only agreed within 4 standard errors, so i was...
  19. K

    Polarization dependace of semiconductor optical amplifier (SOA)

    Hi, could you explain me polarization dependence of SOA amplifiers. and how to transfer the transverse electric (TE) mode to transverse magnetic (TM) mode. Are there any passive components to do it?
  20. A

    Capacitors in Common Emitter Amplifier Circuit ?

    Capacitors in "Common Emitter Amplifier" Circuit ? Should i use Capacitors in "Common Emitter Amplifier" ( CEA ) Circuit ? As i saw many CEA circuits designed without any capacitors there ! And also hear that it's better to use two capacitors, one after the Voltage Source ( that feeds the...
  21. K

    High Pass Amplifier: C & R1 in Parallel

    Is it still a high pass amplifier if C and R1 are in parallel? http://commons.wikimedia.org/wiki/Image:High-pass_active_filter.png
  22. K

    Frequency responce in a common base amplifier

    How the voltage gain of the amplifier depends on the frequency of ac signal. please explain. what is the role of coupling capacitors? how voltage gain is effected in mid , high and low frequency range? thanks.
  23. wolram

    The Pseudo Radiation Energy Amplifier

    http://cn.arxiv.org/ftp/arxiv/papers/0811/0811.0357.pdf The Pseudo Radiation Energy Amplifier (PREA) and the mean earth’s ground temperature Ahmed Boucenna Laboratoire DAC, Département de Physique Faculté des Sciences, Université Ferhat Abbas, 19 000 Sétif, Algeria...
  24. M

    Troubleshooting LM386 Amplifier Noise: Capacitor Value and Behavior Explained

    hi guys, i'm doing the testing amplifier for my DIY project, and i using LM386 IC, i found that is a lot of noise at the output. i saw an example putting a capacitor at the output to reduce the noise, it work! the value of capacitor is 47uF. it not work well for other value capacitor. But...
  25. B

    Differential Amplifier, Single-Sided

    Homework Statement I need to calculate Vo in the image of the circuit (bitmap image link follows): http://www.filedropper.com/circuit" All the information provided is in that diagram - since we are studying differential amplifiers, I assume all the beta values are equal. Homework Equations...
  26. V

    Engineering Integrator circuit using operational amplifier

    I read in a book that perfect integration using inverting op-amp is possible only when the time constant of the circuit(R1Cf) is lesser than the time period of the input signal. I have trouble in understanding this concept. Lets assume i give a square wave as input at the inverting terminal.Now...
  27. K

    Design of differential amplifier

    Homework Statement http://i36.tinypic.com/hugkyb.jpg Homework Equations According to my book, if R3 = R2 and R4 = R1, I can use the following formula: Vo = (R2/R1)(V2 - V1). The Attempt at a Solution We want R2/R1 to equal 5. This means that R3 and R2 must be 5*3,3 = 16.5...
  28. T

    Op Amp inverting amplifier , help

    http://i454.photobucket.com/albums/qq261/integralx2/opamp1.jpg I don't understand why they did something. I found output voltage to be -1.25v , but to find voltage across the 10k resistor, its (Va-Vo)/10k am i correct? cause when i do this and try to calculate the answer for Io its not right...
  29. V

    Most of the op-amps use differential amplifier

    1.My text says 'most of the op-amps use differential amplifier as the input stage.The two transistors must be biased correctly.But it is not possible to get exact matching of two transistors.Thus the input terminals which are the base terminals of the transistors do conduct small dc current'. I...
  30. M

    Remote Volume Control for 2-channel Pyle Pro Amplifier

    Hi, i want to know if there is a possibility to add a remote volume control to this amplifier above. I just have to control the volume of both channels. The buttons themselves don't have to move, just the power should go up and down by the remote. Please let me know if anyone has an idea...
  31. A

    What Is the Nodal Voltage Vb When a 1k Resistor Is Shorted in an Op-Amp Circuit?

    Hi I was just wondering what the nodal voltage Vb would be if you shorted the 1k resistor shown in this pic: http://img401.imageshack.us/my.php?image=opampem4.jpg also with that resistor in place what would the nodal voltage Vb be? i get 90.1mV ty in advance
  32. L

    How to Design a Noninverting Voltage Amplifier for a 10K Load?

    Homework Statement Design a noninverting voltage amplifier which can be varied between 1 and 100 capable of driving a 10 K load to +5V at a frequency of 1KHz. Homework Equations 1. In order to vary the gain should R1 and R2 be 100k potentiometers? Is there another way? 2. For a gain...
  33. S

    Voltage Gain in Midband Region of Transistor Amplifier

    In the midband region the voltage is constant and is assumed to be unity and the transistor amplifier is always used in this region. Doesn’t that mean that there is no voltage gain??
  34. K

    Designing a JFET-JFET Cascode Amplifier: Tips and Resources

    Hi. I'm not actually doing an electronics course (Maths & Physics), but I have just finished building a 140W BJT guitar power amplifier and cabinet. I'm looking to build a FET-FET cascode preamplifier now, but am not too familiar with JFETs - So far, I've got: V+ | Resistor | JFET2...
  35. H

    Designing an Amplifier Circuit for Hypothermia Treatment Device

    Hi, I have project to design a device that measures the temperature of the brain first and then heats the blood to normal tempearture. it is used to treat hypothermia. In hypothermia, temperature of the blood drops down. i have designed a circuit for it. I have attached the pic. It is a...
  36. B

    How to design 2decade BJT-OPAMP cascade inverting voltage amplifier?

    Can somebody help me to find this kind of circuit.im really appreciete your help Specification Only one bjt,one opamp ua741 and asingle power supply of 12v must be used. A 10k ohm load and an input signal will be connected via capacitors to the amplifier. The max voltage gain is about...
  37. M

    Input and Output resistance(CE amplifier)

    Hello people I am trying to revise for my exam next week..I have searched everywhere but still I can't find how to calculate input resistance,stage input resistance and output resistance of a class A common emitter amplifier. any help will be highly appreciated. mathslova
  38. U

    Push-Pull Amplifier Homework: Calculate Vcc, R Input & Gain

    Homework Statement 1. Calculate Vcc and Vee(should be around 14-16). 2. Calculate the input resistance. (You should get a high value). 3. Determine the voltage gain. No calculation is needed. http://img210.imageshack.us/my.php?image=effectampqe2.jpg Ucesat = 1 V Poutmax = 10 W Rl...
  39. U

    Any D/A converter and amplifier for microwave frequencies?

    At a time when pc's come with microprocessors clocked at frequencies of the order of 4 GHz, it must be possible to drive a D/A converter at microwave frequencies. Anyone know of hardware to do this? Anyone know of suitable hardware to transmit the waveform at a power density comparable...
  40. J

    Design a Power Amplifier Circuit for 1MHz Carrier Wave

    i designed an crystal oscillator of 1MHz using MC14069 ic and now i need the design of a power amplifier circuit to increase the power of the 1MHz carrier wave...can somebody help me with this!
  41. F

    Open loop gain of an operational amplifier

    Homework Statement How can the open loop voltage gain of an operational amplifier with AC input voltage be determined experimentally? Supply voltage for op amp is +9V. Homework Equations The Attempt at a Solution I'm really stuck here. I would appreciate some outline of...
  42. W

    Learn How to Build a 2-Stage JFET Amplifier: A Comprehensive Guide

    Hey guys, I am curious on how to set up a 2 stage JFET amplifier. I've reviewed some analysis on 2 stage BJT amplifiers as well as 2 stage BJT/JFET amplifiers but I cannot find anything on how to use 2 JFETs. Any help would be greatly appreciated. Thank you!
  43. D

    Need help understanding Current Draw for a Power Amplifier

    Hi, I'm working on a project with a colleague involving amplifying some simple sine waves (20kHz) using an APEX Microtech Power Amplifier PA50 Two power supplies INSTEK SPS-3610 are connected in series and are supplying the amplifier with +/- 20 volts each. Each power supply can provide...
  44. M

    Non-Inverting Operational Amplifier.

    Good evening. Right. My question is one of a simple nature, I think. Anyways, consider the following non-inverting Op-Amp design: http://www.freewebs.com/mushg/FWThumbnails/OpAmp.bmp Now, the basic formula for any non-inverting opamp is of course \frac{V_{O}}{V_{S}} = 1 +...
  45. S

    The source of noise in amplifier

    hi for every one I am a new member in tis site. I hope from u to help my I have a hmoework so I want some help The question is What is the source of noise in amplifier & how can treat the noise? Thank u
  46. R

    Using a Lock-in Amplifier for Strain Gage Measurement: Tips and Tricks

    hi i am using a lockin amplifier for the 1st time other than a canned college lab demo. i have a 5mV signal from a strain gage that is driven with 10Vpp at 1kHz or whatever i choose. the 5mV is increased to 5.01mV when i add some weight to the arm the gage is weighing. i wanted to increase...
  47. P

    Constructing an IR Amplifier - Is it Possible?

    Is it possible to build an IR amplifier? I have a weak remote aimed a TV really far away. Is it possible to build a device that I aim the remote at, and it amplifies the signal, then sends a copy of the amplified signal to the TV? Pretty much a repeater? If so, how? Thanks
  48. P

    Solving Amplifier Question: Find Vout for a,b,c

    Homework Statement An amplifier has negative feedback applied to it such that feedback fraction is 0.5%. If the open loops gain of the amplifier is 10^5 what is the closed loop gain? I get this as 199.6 The amplifier is connected to a signal source of internal resistance 300kohms which...
  49. P

    Amplifier (non inverting) question

    Homework Statement An amplifier has negative feedback applied to it such that feedback fraction is 0.5%. If the open loops gain of the amplifier is 10^5 what is the closed loop gain? I get this as 199.6 The amplifier is connected to a signal source of internal resistance 300kohms which...
  50. B

    How to Increase Current Output in a Push-Pull Amplifier Design?

    Hi, I need some help with a push pull design. As a project , I am doing a audio cross over. The problem I have is that I cannot find a way to drive enough current into the speakers. For one speaker, the input current is 0.02 [A] and after the push=pull amplifier, I need to be able the...
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