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. M

    How would I draw this non-inverting amplifier?

    Summary: So far, I have only dealt with ideal operational amplifiers, so I am kind of lost trying to visualize how a practical op amp should look like. A non-inverting amplifier with a gain of 10 uses 100K as its feedback resistor. It gets its input from a signal source whose source resistance...
  2. M

    Calculating Component Values in this Low-Frequency CE Amplifier Circuit

    Hi guys , i need help. How do i calculate C1? fu=25Hz
  3. Terrycho

    (Bipolar Junction Transistor) The Current Gain of Common Base Amplifier

    Everything is okay besides the current gain of this circuit, which is "g" there The formula of current gain is I_out/I_in If I call the current flows to R_e I_2, according to KCL, the following formula must be satisfied. I_in + (β+1)I_b = I_2 Therefore, to know I_in, we should use the...
  4. T

    Capacitors needed when using an audio amplifier?

    Hello, I am using this little audio amplifier with my Maximite computer: https://www.amazon.com/dp/B07MQ44KLP/?tag=pfamazon01-20 I know that it's a best practice to use capacitors on the audio output from amplifier chips to filter out any extra DC current. I am under the impression that the...
  5. C

    Class A Amplifier Sinusoidal Input/Output Relation

    My simplistic derivation below for a Class A amplifier shows that an AC signal at the input produces DC, fundamental, and 2nd harmonic terms at the output. This seems to contradict most the information I have found on this - which just states that the output is sinusoidal and of the same...
  6. T

    PCB design and schematic for a half bridge power amplifier

    Hi, I am making a half bridge power amplifier that operates at 24 V. The bridge has to supply around 3A current to an inductive load (10mH) The bridge will be controlled using 20kHz PWM from a microcontroller. I have put a ACS712 current sensor in the load path to give feedaback to the...
  7. Callum Plunkett

    Quiescent output of a JFET amplifier

    Homework Statement I am to construct a JFET amplifier with Pspice (SIMetrix) to determine the quiescent output and to compare it with my own calculations. However my calculations don’t match the simulated output by quite a margin. Can anyone point me in the right direction as I’ve had very...
  8. TechTree

    Electronics Can I Convert My Guitar Amplifier into a Bluetooth Device?

    Hello, I have a guitar amplifier I'd like to convert into a bluetooth device. Using it's current power supply and allow it to receive a bluetooth input. I have a bluetooth speaker that I took the electrics from. The bluetooth speaker is digital, but when it outputs to the speaker it's an...
  9. Z

    Engineering Amplifier circuit driving an 8 Ohm speaker

    Homework Statement Hi all. I need a bit help with the following. Estimate the power developed in the 8 Ω speaker of the circuit of FIGURE 2 for a 1 kHz sinusoidal input signal of 100 mV peak. All capacitors may be assumed to act as a short circuit at the frequency of operation. Compare your...
  10. A

    B The Gain of the Inverting Amplifier and Virtual Earth....

    This is an inverting amplifier incorporating an ideal op-amp with infinite open loop gain. I have a simple question concerning the derivation of its gain (-R2/R1). The point I circled is at 0V (Virtual Earth) but then, if V+=V-, Shouldn't Vout=0 regardless of what R2 and R1 are?? What's wrong in...
  11. Boltzman Oscillation

    How can I analyze this transimpedance amplifier?

    Homework Statement The opAmp network shown in figure 68 is a transimpedance amplifer that employs both negative and positive feedback. Assuming that the op-amp is ideal, calculate the value for the output voltage for Jg is 1mA.The circuit and question are this...
  12. A

    Voltage Gain of a common-emitter amplifier

    Hi, i have a problem with the voltage-gain of a common-emitter-amplifier. I have calculated the theoretical value of the gain given by ##G=\frac{\partial U_{a}}{\partial U_{e} } = -h_{FE} \frac{R_{c} }{R_{v} }## , which is between -13925 and -7311 for ##420\leq h_{FE} \leq 800## (given by the...
  13. C

    Transfer Function of a FET Differential Amplifier

    Homework Statement [Taken from Razavi's Design of Analog CMOS Integrated Circuits 2nd edition]Homework EquationsThe Attempt at a Solution [/B] I'm not too sure what to do with this question. Here's what I think of the circuit This doesn't look like a differential amplifier to me since...
  14. M

    Hi, how to make 2 IF from one IF amplifier circuit, to get higher gain

    Hi, i take one If amplifier, from internet and i want to make the second the same, but i don't know how to couple, of what i need to do, to get more gaing can somebody help me? here is one IF amplifier in ltspice, rename in asc, or remove only txt extesion. and what is the best to do, is for fm...
  15. CharlieCW

    Degenerate parametric amplifier: quadratures

    Homework Statement The degenerate parametric amplifier is described by the Hamiltonian: $$H=\hbar \omega a^\dagger a-i\hbar \chi /2 (e^{(2i\omega t)}a^2-e^{(-2i\omega t)}(a^\dagger)^2)$$ Where ##a## and ##a^\dagger## as just the operators of creation and anhiquilation and ##\chi## is just a...
  16. R

    What's the advantage of using a voltage buffer amplifier?

    i want to understand what's the advantage of using a voltage follower
  17. N

    High Power Amplifier for Acoustic Transducer

    Hi all I am in search of a Power Amplifier (preferably Solid state pulsed amplifier ) which is able to output around 340 Vrms across 25 ohm impedance load (acoustic transducer operating at approx 4.5 KW) in pulsed mode with duty cycle less than 1%, maximum pulse length of 5 ms and operating...
  18. M

    Hello, can somebody check my transistor amplifier schematic?

    Hi, can somebody tell me how to connect some component in this picture, i draw it but is not working because i have no bfg520 transistor, look this picture maybe i make mistake
  19. maven sharma

    Integrating operational amplifier

    Homework Statement Calculate the output voltage of the amplifier 2. Homework Equations [/B] https://www.electronics-tutorials.ws/opamp/opamp32.gif The Attempt at a Solution I do not know how to approach a circuit with RC in series to inverting terminal of integrating op amp
  20. A

    Input resistance into a MOSFET amplifier

    Hello everyone I was hoping you could help me with something, in my analog electronics course.. In the diagram below, is displayed a circuit and its equivalent... I don't understand why the input resistance is only the parallel combination of R1 and R2?? Why doesn't Rsi contribute to the...
  21. A

    Where to Learn how to Design Circuits?

    Hello, I'm currently getting my degree in mechanical engineering but have lately taken an interest in electronics. I've ordered several books and have learned a ton about resistors, capacitors, transistors, diodes, etc. However, every circuit I have made so far has been one that somebody else...
  22. C

    MOSFET Common-Source Amplifier Small-Signal

    Homework Statement Hi, so I was trying to derive the small-signal model of a common-source mosfet amplifier that I learned from the notes. Here is what I did, Now the issue is the i_d branch in the final small-signal circuit. In my lecture notes, that i_d branch is not there at all but...
  23. C

    Cascode Amplifier Small Signal Model

    Homework Statement Hi, I'm just trying to derive the small-signal model of the cascode MOSFET amplifier circuit. In the lectures, we were just given the small-signal model directly. I'm trying to derive it. I have almost the exact same thing except where I put the output voltage. In the...
  24. B

    I High energy laser-electron inerraction same as in TWT amplifier?

    Isn't the high energy laser-electron interaction described in the following article and citation, the very same principle used in the classical TWT amplifier? https://phys.org/news/2018-02-intense-laser-evidence-electrons.html https://journals.aps.org/prx/pdf/10.1103/PhysRevX.8.011020
  25. rishi kesh

    How does an opamp work as non-inverting amplifier

    Homework Statement I am doing a little bit of research about op amps. What i know so far from the book it that op amp have a very large open loop gain. To reduce the gain to desired amount we need resistor which connect output to invering terminal(negative feedback). Homework...
  26. N

    Intermodulation in an Amplifier and Third Order Incercept

    Hi, I have measured a Transfer function curve for an amplifier, showing Input power vs output power. It shows non-linear increases for a portion of the transfer curve (at higher input power). I also measured 3rd order intermodulation products during the input power range where it gives non...
  27. N

    Power Series Equation for Amplifier and Harmonics

    Hi, I keep reading in multiple sources that amplifier output can be given by Vout = a0 + a1v(t) + a2v2(t) + a3v3(t) + ... + anvn(t) I've checked in three of my textbooks and there is not a clear definition (its often just stated) why this equation is used and why it works. I am not looking...
  28. C

    Trouble with getting AM receiver to work

    Hello, I have assembled the following AM radio reciever circuit: Purpose of the circuit: To receive AM radio signals and provide the output audio of these signals ( demodulated ). Circuit elements: L ~ 1.5mH , C ~ 300pF , Amplifier IC: LM324N , Diode: 1N4004 ...
  29. J

    Transistor : Output voltage of the amplifier

    Homework Statement Homework EquationsThe Attempt at a Solution This is a solved example given in my Physics textbook . I am not understanding a couple of things . 1) How is Iin calculated as Vin/Rin ? Why is the book not taking potential difference between Base Emitter into consideration...
  30. nothing909

    Expression for closed loop gain of differential amplifier

    Homework Statement The question is Derive an expression for the closed loop gain of the differential amplifier. I have solutions for these questions but the solution for this question is quite vague. Here is the solution: I understand part 1 and part 3, but part 2 I don't. So looking at...
  31. nothing909

    Instrumentation amplifier practical results vs simulation

    I just have a simple question to ask. I'm simulating an instrumentation amplifier and then testing it practically. When I simulate it, my gain is 6, but when I test it, I get a gain of 5.54. I'm just wondering what is causing the slight drop in gain in the practical results?
  32. nothing909

    Testing instrumenation amplifier

    Homework Statement I just have some very simple questions to ask. I'm testing a basic 3 OP instrumentation amplifier I have to short V2 to ground and test V1 from -2V to 2V, in 0.25 increments. I then have to short V1 to ground and test V2 from -2 to 2V in 0.25 increments. the results i...
  33. epenguin

    Constancy of audio power from battery (hearing aid)

    I have recently had to adopt hearing aids. I shall soon be taking them back to supplier for adjustment/repair/replacement of one of them. What seems to happen is that with new (lithium) battery it gives sign of life and some amplification into the right ear, but after a few hours there is no...
  34. D

    Differential Amplifier with negative feedback

    Homework Statement [/B] Homework Equations Adiff(single-ended)= 1/2gm*ro||Rd β=R2/(R1+R2) The Attempt at a Solution I am really confused as to how to find A. I know the feedback of the circuits around the R2 and R1, but I don't understand how the open loop gain can be found. Can someone...
  35. F

    How a positive Feedback Amplifier works?

    In a positive feedback amplifier, as I understand, output of the amplifier is fed back into the input of amplifier, essentially creating a loop. My question is specifically, how the loop does not go in an infinite cycles ? what prevents it from going into an infinite loop ? How many cycles...
  36. A

    Actuating Pencil To Draw Waveforms

    I am looking to make a pencil whose tip moves to create a waveform as you move it across the paper.In essence, I want to be able to record a sound and then play the sound through the pencil whilst I draw with it, of course, I will use software to lower the frequency to make it more of a waveform...
  37. Pushoam

    Measuring the output from a Transistor Amplifier

    Homework Statement I understand that the DC current will not flow through the capacitor once the capacitor gets fully charged. So, after a long time , only AC component of the net current flow through the capacitor. How to show that all of the carying voltage appear across the capacitor...
  38. Pushoam

    Voltage amplification done by a transistor amplifier

    Homework Statement Homework EquationsThe Attempt at a Solution The equivalent circuit is drawn below. It is assumed that the potential drop across the pn junction in forward bias is 0 V(I can't take it 0.7 V as the input voltage is 0.5 V). In this case the p-n junction is equivalent to a...
  39. D

    Optimizing Mosfet Amplifier Problem Solution with Kirchhoff's Law and KVL

    Homework Statement [/B] Homework Equations K=0.5μnCox(W/L) ID=K×(Vgs-Vt)2 Kirchhoff's voltage Law The Attempt at a Solution For part A, My initial assumption was that since we are trying to find the DC bias current(to help find K), we would use the large signal, where capacitors are...
  40. M

    Noise I'm getting in my summing amplifier

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > I am measuring EC of solution . I got Vec is 0.98V . After that, I took it to summing amplifier to reduce error from measurement . However, I saw a problem is that Vout of summing amplifier was...
  41. M

    Hello everyone, can somebody with cascode amplifier

    Hello evervone can somebody help me, to calculate the cascade amplifier, if somebody can tell me the formula? of to explain me? i am reading the book "electronics devices circuit and theory" page 201-202 i don't know how come the value 2.50v, 1.25v, 1,87v see the photo down...
  42. K

    Opamp for MF/RF ranges (1.0-1.2MHz)

    Hello! I have a bit of trouble finding general op-amps that can amplify at medium frequency ranges, and with a good enough gain of 200 or 46dB. My max desired operating frequency is around 1.2MHz so I don't really care if it no longer amplifies much at frequencies higher than this. I am aware...
  43. Andres kubliki

    Understanding Output Changes with Sensitivity on SR830 Lock-In Amplifier

    Does somebody knows why the output changes with the change of the sensitivity? When I'm measuring noise, let say I have a value of 5nV/sqrt(Hz) at 10 nV sensitivity. When I switch to 20 nV, the output goes to 10nV/sqrt(Hz). Why? Which on is them the correct?
  44. wolram

    Help with finding vintage valve amplifier circuits (amplifiers for a rock band)

    Can anyone help please, I have been searching for vintage valve amplifier circuit diagrams and components. I need help in finding valves, transformers, and diagrams. I intend to build amplifiers for a rock band so i would like to build one with a 3KW output if that is feasible. Thanks for any...
  45. R

    MAR-6 MMIC amplifier chain saturation?

    Hello. I have devolopped a line amplifier with 3 x MAR-6 MMIC. Normal daisy chain is : antenna followed by a LNA which is followed by my line-amp. If nothing is connected at the input ofLNA, all 3 Mar-6 have normal operating voltage ie 3.5 V and resulting noise is very low (seen with a 100 MHz...
  46. B

    Are load cell signal conditioners limited to sample speeds?

    Hi, I need to buy a bridge amplifier for my load cell. I need to be able to take at least 350SPS (samples per second). The only load cell amplifier I can find within my budget states that it has a selectable 10 SPS and 80 SPS output data rate. Heres the link to the amplifier...
  47. Z

    Increasing voltage using operational amplifier

    I want to build own circuit usinghttps://ez.analog.com/external-link.jspa?url=http%3A%2F%2Fwww.kynix.com%2FProduct%2FCate%2F470.htmland resistors. I have 12V power source (car accumulator) and 6V input voltage (Vin). I want to get 12V Vout and 25W at the output. So that is about 2A...
  48. D

    Finding the transfer function for a difference amplifier

    Homework Statement I need to find the transfer function of the attached circuit (this isn't a homework question so I don't know if there's even a solution, but last time I posted this type of question on the EE forum, it was redirected here)Homework Equations I know it needs to be eventually...
  49. Nikhil N

    How to choose an amplifier to couple the noise into data line

    Hii... I have to couple the noise into a communication cable for analyzing the performance of the communication. I am using a function generator which will generate a white noise of 1-2V(rms) and I have a current transformer to couple this to the communication line. The current transformer has...
  50. Nikhil N

    What is the meaning of 30W amplifier?

    When I have gone through spec of amplifier, I saw 30W for output. Is it mean that even if I am connecting a load of less impedance, say 30ohm, will I get 30V output voltage across the load?
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