What is Amplifier: Definition and 557 Discussions

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. T

    Help with a simple amplifier design for an audio signal.

    Hi, I'm designing an amplifier and need help with some basic ideas (Filtering is already taken care of). My main question is bolded. The output is an audio signal, and it drives an 8 ohm speaker. The power is 1 watt through this speaker. The input signal is coming from another amplifier...
  2. B

    Hhow an NPN transistor can be used as a small signal amplifier?

    Hi, Could someone please help me with something i need to know to complete my college course? The question says: 'Show with the aid of a circuit diagram and input/output waveforms how and NPN transistor can be used as a small signal amplifier, when operating in a common emitter...
  3. P

    BJT amplifier frequency response.

    Today I did a lab on BJT amplifier frequency response. I got the fc1 and fc2,BW and F0 center frequency. The band pass turned out to be asymmetrical. What i want to know is this. Input V=40mVpp output V=2Vpp cut off V=1.41Vpp When I turned up the frequency to 2fc2, i got about...
  4. M

    Non ideal Operational Amplifier problem

    hi... can anyone help with the problem i attached thanks in advance... I think a good start would be to convert the current source into a voltage source
  5. J

    How can I filter and convert a differential current output from an amplifier?

    Hello Guys, I really need some help with this one. I'm still working on the circuit design for this AD9959 programmable pulse generator and I found (from reading the datasheet) that the output from the DAC uses differential current output and not voltage output (something like 0.5V @ 20 mA...
  6. E

    Solving the Filtered Amplifier Puzzle

    Homework Statement We have a filtered amplifier (diagram is attached). We do not know Cf or Rf. We know that: 1 volt input at 5 Hz = 9.25 volt output 1 volt input at 200 Hz = 6.77 volt output 1 volt input at 500 Hz = 3.66 volt output Homework Equations The transfer function for...
  7. I

    Massive Short Wave Amplifier

    Is there a limit to the possible amplification of Short Wave radio transmission and/or reception? A friend of mine wants to build a massive amplifier / transmitter. If a limit does exist what is the physical law used to explain it?
  8. C

    Connecting an IPod to an Amplifier: Troubleshooting Tips for a Last-Minute Party

    I've got a sony home theater system and my dvd player has gone for repairs. I've got a party to throw by tomorrow and I need some help. I want to connect my IPod to the HT system. The only problem is, it takes those individual inputs for the left and right audio signals (red and white wires)...
  9. P

    Another transistor amplifier problem

    http://www.vcaa.vic.edu.au/vce/studies/physics/pastexams/physicspilot12004.pdf Page 13. AC signal on CRO. Answer is B. How the heck do they do that? Relevant information is on page before. Love peoples explanations but please try to keep it simple. Sorry if i seem direct. I don't...
  10. F

    Solving Transistor Amplifier Question from 2006 VCE Physics Exam

    My year 12 exams are in 1 week exactly and I'm worried about a question (from last year's exam) that my teacher can't even answer. Each year they tend to repeat the difficult questions, and this was one of those. I'll just give a summary of the question, and maybe you'll be able to answer my...
  11. A

    HIGH o/p dual power amplifier ( HELP )

    HIGH o/p dual power amplifier (! HELP !) i have attached the cct diagram i found about this IC BA5417 it is a power amplifier as one can see pins 11 & 12 are input but how exactly does on give this input i plan to give input from my discman so there will be one ground wire and the two...
  12. K

    Solving a Basic Amplifier Circuit - Get Help Here!

    Hello every body I am new members in here I hope you will eccept me as a good member I study electronic in college... I have got this task and I can't answer it The reason why because the tutor didn't explain to us how it's work ... he wan't us to answer it using the...
  13. M

    Can I Use a DAC to Control the Amplitude of a 2V Square Wave with AC Coupling?

    So here is the deal: I am driving a polarization rotator to attenuate light. The polarization rotator takes a 3-5kHz AC signal, they suggest a square wave. I have a frequency generator chip that can generate a 2Vpp signal, but I want something a signal of 0Vpp-10Vpp (though most of the...
  14. J

    Where can I find an intuitive tutorial for building a tube amplifier?

    Hello All, I'm working on a three-channel tube amplifier for some experiments I'm doing (and later on, my keyboard :biggrin: ) and I was wondering if the nice people here could give me some tips for the circuit construction. I've already ordered a bunch of 6au6 tubes (because they were 50...
  15. E

    Understanding Input and Output Resistances of an Amplifier with Feedback"

    Hi, Suppose I have an amplifier with feedback, how would I measure the input and output resistances (using instruments)? If the input of the amplifier is a voltage source, the input resistance would simply be V(signal) / I(signal). Now if the output of the amplifier is a current, would I...
  16. S

    Working of BJT as an amplifier: concept

    How does a small change in base current result in a large change in collector current in a BJT? Please explain in terms of movement of electrons (in NPN). Most textbooks I have referred say that the reason is low resistance of emitter-base and high resistance of collecter-base. However i cannot...
  17. Amith2006

    Inverting Operational amplifier

    Homework Statement 1) Consider an inverting operational amplifier as shown in figure. Suppose R1= 1000 ohm & Rf = 10^6 ohm. It is said that the input impedance=R1=1000 ohm and the Output impedance= 0. 2) Consider a non inverting operational amplifier as shown in figure. Suppose R1= 3500...
  18. M

    Output Voltage Calculation for Difference Amp Circuits

    I know the output voltage for a difference amp is (R2/R1)(V2-V1) but how do you find the output voltage when you connect the circuit attached to the difference amp where V1 and V2 are the input voltages to the difference amp?
  19. E

    Engineering Analyzing an AC Amplifier Circuit with Negative Feedback

    Homework Statement The problem states that we should draw the Vout curve of an amplifier circuit. Homework Equations We have a sinusoidal sign with amplitude=1v and frequency=0.5 v(t)=A*sin(2pi*f*t) f=1/T T=2s The Attempt at a Solution Since we have negative feedback...
  20. E

    Operational Amplifier with positive feedback problems

    Homework Statement I have some problems determining the tension output value for this circuit and this confusion comes from the presence of positive feedback and an alternate current.Since I'm used to negative feedback circuits and direct current it confuses me a bit,so any help is deeply...
  21. E

    Engineering How Does NTC Thermistor Resistance Relate to Tension Vt in an Amplifier Circuit?

    Homework Statement One of the problems question is: Determine the analitical expression that relates the resistive value of the NTC thermistor with the tension Vt.I've come to an expression but I'm not sure if it's correct.Also, the other question of the problem is: Make an analitic...
  22. 2

    Need a DC power supply - amplifier?

    I need a DC power supply for a project I'm working on. I have a Leach amplifier with a monster power supply and heat sinks able to handle it clipping at ~500W/channel. It's just sitting on my floor. I also have a 2 16bit 1MHz DACs and 2 16bit 200KHz ADCs attached to a National Instruments...
  23. E

    Differential amplifier simulation

    I'm trying to simulate this ciruit on microsim schematics: http://i75.photobucket.com/albums/i281/esmeco/amplifier.jpg This's what I've got so far: http://i75.photobucket.com/albums/i281/esmeco/Microsimcircuit.jpg What I want to see is the final graph with the values of V0,V1,V2.V1...
  24. Z

    Question about Inverting Amplifier

    Just a simple question about the Op-amp. For inverting amplifer circuit, if I connect the positive terminal of the power supply to the Vcc, and the nevgative terminal to the Vee. What will happen to out put signal related to the in-put signal? Thanks.
  25. E

    Amplifier voltage output error

    I've assembled an amplifier circuit which is composed by a V1 and V2 input and Vo output.V1 is 1V and V2 varies from -5v to +7v with increments of 0.5v. The formula for Vo is: Vo=(1+R2/R1)x(R4/(R3+R4)xV2) - (R2/R1)xV1 My questions are:why does the equation |Vo experimental - Vo theory|...
  26. E

    Differential Amplifier Equations for Vout Determination | Amplifier-1.jpg

    Hello! I'm trying to determine Vout on this amplifier and I'm having some problems with the equations,because I'm not sure if they're correct! This's the link to the amplifier: http://i75.photobucket.com/albums/i281/esmeco/Amplifier-1.jpg The equations I've got so far are these: IB=0...
  27. P

    Common Mode Differential Amplifier

    Hi, does anyone know what are the 4 different cases in a common mode differential amplifier? thanks a lot for all of your help. thanks, peace
  28. D

    Computer Amplifier: Designing a Multiple Stereo Output System

    Hello, I have a few questions about creating a multiple output stereo computer speaker amplifier. I am using a standard audio output from the computer. Basically what I want is to have: 1. Both quarter inch and eighth inch stereo jack input, but only one at a time will be used. I...
  29. D

    Designing Audio Amplifier with BJT and MOSFET Components

    Hi, I'm new here. can somebody put here an a schematic of Class AB, D,G or T. I need an audio amplifier that work with bjt and mosfet simultaneously, i think that kind of amplifier is class g, but I'm not sure,for example i saw an 5000w amplifier with 2sc5200 and his pnp pair working with...
  30. T

    What chip can I use to boost IR signal for my projector?

    Right now we have a projector and it is about 75 feet away. The remote, well, works pretty terribly to say the least. What I would like to do is build an IR amplifier to boost the signal so that the projector can pick it up much easier. What I plan to do is use some sort of buffer/driver IC...
  31. A

    Can anyone suggest an amplifier design that meets specific requirements?

    Hey, I need to design an amplifier using either BJTs or MOSFETS (or both) that meets the following requirements: Overall voltage gain: 800 Input impedance : 200Kohms Output impedance: 200 ohms Frequency band width: 10MHZ Can anyone help me with what kind of arrangement of amps can...
  32. D

    Modeling the Input Impedance of an Amplifier

    I'm trying to model a circuit. Part of this circuit is a guitar amplifier. I don't know what kind of circuitry is inside the guitar amp, it manufactures often list the input impedance in the product specifications. When they say input impedance, do they mean the impedance between the...
  33. A

    How do resistor values affect the operation of a BJT transistor?

    I'm really confused between saturation and amplifier. When will the transistor work in saturation mode and in amplifying mode? Resistors are the matters. We chose the resistors so that the transistor will work in saturation or amplifying. How can we chose?
  34. S

    What is an Electrogastogram Amplifier and how is it used in medical research?

    Hello... How are you all... I have this research about Electrogastogram Amplifiers, If anyone has any idea what this amplifier is about please reply. Thanks for your time... SCHNiTZER :rolleyes:
  35. D

    Optimizing MCA Amplifier Gain for High Energy Resolution: A Case Study

    A radioactive material emits 2 gamma rays with 2 energies 50 keV and 200 keV with equal probabilities the detector system has a quantum efficiency of 100% and 50% respectively at these 2 energies and the pulse heights are 1.0 mV and 4.0mV respectively. The pulses are input into a 512 channel, 10...
  36. D

    What is the appropriate gain for the MCA amplifier in this scenario?

    :mad: A radioactive material emits 2 gamma rays with 2 energies 50 keV and 200 keV with equal probabilities the detector system has a quantum efficiency of 100% and 50% respectively at these 2 energies and the pulse heights are 1.0 mV and 4.0mV respectively. The pulses are input into a 512...
  37. denian

    Engineering Common emitter amplifier circuit using feedback biasing

    i don't have the basic of analog, but i tried to look for in the books. unfortunately, the books are using voltage divider biasing instead of feedback biasing. i have a circuit like this: http://www.mrnerdy.com/forum_img/BJTampfeedbackbiase.jpg would anyone tell me the flow of the current in...
  38. electronic engineer

    Operational Amplifier Course - Topics and Tutorials

    I want to inform you that our course about operational amplifier at university has such of the following topics: adder amplifier(inverting and non inverting)- integrator-diffrentiator-comparator- schmitt trigger-rectangular waveform generator-triangular waveform generator...and some active...
  39. J

    How to Use a Lock-In Amplifier for Johnson Noise Experiments

    Is there a book or website that explains throughly how to use a Lock In Amplifier? I have never used one before and am using it in a Johnson Noise experiment with the "Art of Experimental Physics by Preston and Dietz" acting as the lab manual.
  40. M

    Testing an Inverting Amplifier Circuit with R1 = 10k and R2 = 100k

    I have attached an image of an inverting circuit. If I set R1 = 10 k ohms and R2 = 100 k ohms, I need to verify if this circuit works or not. Therefore, would the voltage between points A and B be equal to 0.1 V since B is connected to ground? The voltage input is 0.1 volts. Thank you
  41. M

    Maximizing gain in a bipolar transistor amplifier: capacitor vs. resistor

    I have the amplifier in the attached file and I measured Vout without any input and got a really big number. Should it be really big or really small? I mean theoretically, what should it be equal to because I'm not sure that my answer makes any sense. Thanks!
  42. S

    Operational Amplifier (Voltage Follower)

    Hi Guys, I'm trying to amplify a millivolt signal from an electrode that has a high input resistance (~ 200 MOhm). To avoid losses over the series resistance I'm using a high input impedance Op Amp TL071CP as a voltage follower. The problem I'm having though is that for some reason when the...
  43. C

    What are the Answers to Operational Amplifier Questions?

    hi there, i have two questions concerning operational amplifier which i can't figure out. i have tried them for hours, and finally get on a bit, yet i am not sure whether i have the answer right. :( 1a. What is the value of the feedback resistance in figure 1? My ans: V_out/ V_in = 1+...
  44. A

    Transistor as switch-op amp voltage amplifier?

    Hi can anyone explain to me how you can drive a transistor to function as a switch?what calculations i have to make in order to decide the type of transistor that i need and the kind of resistors that i need. also i have a voltage of maximum 80 mv.i want to enlarge it in order to drive the...
  45. S

    Understanding Component Functions in a Common Source Amplifier

    Just out of interest guys have I got this right? Function of certain components of a common source amplifier: Capacitors at input and output: They are coupling capacitors and simply block the DC voltage, but allow the AC voltage through. Gate Resistance: Is the purpose of this to limit...
  46. S

    Load Resistor in a MOSFET amplifier

    Hi Guys! well! i have designed a mosfet amplifier. This amplifier uses only MOSFET in its operation along with an input signal and capactors and resistors and VDD. I want to ask u one thing. The amplifier which i have designed takes 0.1V of AC signal as an input and provides a gain of...
  47. E

    How does a step function affect the output voltage of an ideal OP-AMP?

    I am given an ideal OP-AMP like this (R-resistor, Cap-capacitor): ____+Cap-_ | | ___R____|__|\______|_____ + | -|/ + | V in | V out - | | | |_________|______________ - and V in is...
  48. L

    Build Simple Amplifier w/ Photodiode (No Op-Amp)

    Does anyone know how to build a simple amplifier to use with a photodiode that doesn't involve using an op-amp? Thanks.
  49. C

    Instrumentation Amplifier question

    Hi, Just a little question. The question wants me to obtain an expression for v0 as a function of v1, v2 and vcm, and show how the commom mode signal vcm can be canceled from the output by a proper adjustment of one of the resistors, R3, R4 or R5. To find v0, I have to apply the theory of...
  50. S

    Question regarding electronics (operation amplifier)

    I have my question,solution and doubt in the attachment that followed.Thanks for anybody that spend some time on this question.
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