What is Amplifiers: Definition and 104 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. E

    Engineering Unable to model Transresistance amplifier with feedback correctly

    I spent the whole day trying to figure why transresistance amplifier modelled with z-parameters does not match with nodal analysis results but I sill can't figure out. I desperate need help on this... I write down step by step what I did for a very simple transresistance amplifier here and hope...
  2. E

    Is 2010 the beginning of stable period for amplifiers?

    I noticed some equipments amplifiers were designed in 2010 and they are still using the same components or chips now. Whereas those made in year 2000 are already obsolete by the 2010s. Does it mean there is not much improvement in amplifier, op-amps or instrumentation amps between 2010 and 2024...
  3. D

    Design an opamp circuit with this transfer function on 3 voltage inputs

    TL;DR Summary: Build a circuit of given operation on voltages I'll appreciate any help. I need to create circuit of this operation on three voltages: We'll use circuit of voltages summer: The third term is the integral of U_3, so we'll use integrator: Than, calculate capacitance: And on...
  4. Stonestreecty

    Heavy Amplifier Circuit Oscillation Happened

    Hi, all I am experimenting with audio amplifiers for a while now. I learned how to do an operational amplifier with discrete components and understand all its section and sub-circuits, recently. Then I decided to just skip the hard part and use operational amplifier and output power stage for an...
  5. Narayanan KR

    A Different Way to Achieve Electron Velocity Modulation in a Klystron

    Please Notice That the Toroid Coil is Outside the Discharge Tube and yet able to influence electrons moving inside the Tube.
  6. Jason-Li

    Operational Amplifiers & Resistors to form a Black Box

    So basically I am trying to give an output of Vo = 10(V2-V1) From Figure 9 Example Gain of first Op Amp = Rf / R1, if R1 & R2 are equal. What's throwing me off is using 5 resistors to create a circuit rather than 6 or just 3. My initial thoughts were the following: To use the first loop...
  7. paulmdrdo

    Transformer Coupled Class A amplifier Single supply

    How can Vce vary from 0 to 2Vcc? In class, I learned that it was due to Lenz Law working in the transformer and a voltage of Vcc being induced to reverse the change in Ic. However, I cannot picture this. Can someone please explain with a diagram of how this comes about in the transformer windings.
  8. J

    Generating a rising staircase waveform using an integrator?

    Summary:: My understanding of integrators and the waveforms they generate is hazy. The question I am trying to solve is : Sketch the output waveform for an inverting integrator if the input signal is a square wave with amplitude 5 V and frequency 1kHz where the product of Resistance and...
  9. Saptarshi Sarkar

    Intuitive way to understand ideal current and voltage amplifiers

    I was reading about ideal current and voltage amplifiers and the book says that an ideal current amplifier should have 0 input impedance and infinite output impedance while an ideal voltage amplifier should have an infinite input impedance and 0 output impedance. I am not quite sure I...
  10. F

    Current and Voltage amplifiers

    Hello, Basic question: what is the difference between a current and a voltage amplifier? Naively, in principle, I would think that if either quantity is magnified, the other will be also magnified simultaneously. How can we magnify current without magnifying the voltage and vice versa? Thanks...
  11. R

    Sawtooth wave generator from operational amplifiers

    Homework Statement Homework Equations See above in the question The Attempt at a Solution I know that I need to be using a summing amp with the sinusoidal terms but I am struggling to calculate the input values that I need, also I think I need a capacitor in place of R6 but I'm not...
  12. J

    Operational Amplifiers Homework Help: Get 20V Output in 2 Hours

    Homework Statement http://prntscr.com/kjbhim Okay, so I need to draw an op-amp circuit that'll give a 20V output but I have no idea how to start this and this is due in two hours. Could someone please point out to me how to start this off? Thank you so much. Homework EquationsThe Attempt at...
  13. C

    Calculating Required Gain for Fifth Intermediate Amplifier

    Homework Statement FIGURE 1 shows the block diagram of a superhetrodyne radio receiver. In a test a 20 μV signal was fed from the aerial into the first stage of the receiver, a radio frequency amplifier. This signal is the passed through several stages of the receiver to eventually appear at...
  14. A

    What are the values of Rf and V2 for the given circuit?

    Homework Statement Hello, I am trying to Calculate The Resistance Rf and the value of the Voltage V2. The setup is a logarithmic Op amp connected to a differential Op amp. Both Op amps obey the Golden Rules. Attached below is my attempt at the solution and the question. Currently, I have an...
  15. N

    Power Ratings of RF Amplifiers

    Hi all I am studying RF amplifiers data sheets and there is some confusion i am facing in its specifications. One such amplifier claims Power Output at 50 ohm load with 20% duty cycle to be 2 KW. However, the minimum gain it specifies is 63 dB and maximum input it claims to be 10 dBm (around...
  16. Jayalk97

    Good resources to practice transistor amplifiers?

    Hey guys this isn't so much a homework question as it is a learning question. Any good resources online that could help me practice calculating current/voltage gains as well as input/output resistances for BJT and MOSFET amplifier circuits? I can't really find any resources that give me problems...
  17. OldWorldBlues

    Trouble understanding common-emitter amplifiers

    Hi there! I've been tinkering with some homemade speakers, and wanted to make a simple amplifier circuit to step up the some 3 volts that comes out of an aux jack to 9 or 10 volts. I decided that the common-emitter model looked the easiest to understand. I was mistaken. This is the simplest...
  18. N

    High power low frequency RF Amplifiers

    Hi all I am searching some commercially available industrial grade power amplifiers: 1.In the frequency range of 80 KHz to 140 KHz with output power of 2 KW to 50 ohm load in pulsed mode (<10% Duty Cycle 2.In the frequency range of 400 KHz to 450 KHz with output power of 5 KW to 25 ohm load...
  19. Hugo_Researcher

    Research on Lock-in Amplifiers

    Dear Physics Forums, For a research we are conducting, we're seeking some input from users of a Lock-in Amplifier. If you use a Lock-in Amplifier, could you provide me with a few answers to the following questions? What's your overall experience with lock-in amplifiers? Have you encountered...
  20. G

    Understanding High-Pass Filters and CE Amplifiers

    So I wanted to make something clear. I really posted too much threads this week, but that's for the purpose of learning. So a CE Amplifier has a blocking capacitor which together with the input impedance forms a high pass filter. But what I think is this filter is a high pass one only when the...
  21. H

    Op Amp Basics: Why Does It Not Input Current?

    Ah, the op amp... so easy to learn. Yet i have a question: Why the op amp does not input any current? Is it made by some sort of CMOS technology?
  22. N

    Frequency analysis of transistor amplifiers

    Hi guys, I am trying to do this question on my own but i am not confident if what i am doing is correct. please download the Question2.docx file and my workings are in blue. hope someone can help me with this. 1. Homework Statement A. For circuit (a) below, calculate: R_e and R_C to make...
  23. F

    Amplifiers, transistors and opamps

    Hello Forum, I have recently learned about transistors and their ability to control (amplify) other signals. BJT transistors amplify current. There are also FET transistors. Some devices are termed current-controlled and others are called voltage controlled. Are there amplifiers that amplify...
  24. Fawkes

    Do class F amplifiers work in linear mode or CCM?

    Hey guys, I am dealing with a slight issue here, I am learning the basics of class F amplifiers. but I am not able to understand that whether the transistor in class f operation works in linear mode or current control mode? Also i am dealing this problems at power levels of 10W to 25W scales, if...
  25. K

    Electronics: push-pull amplifiers

    I am writing a paper on Classes A and B push-pull amplifiers and was wondering if anyone would be willing to share some valuable insight into this type of circuit, i.e. advantages, disadvantages, when and where they can be used, etc.. Also, I have been doing a lot of my own research into this...
  26. I

    Electrical Engineering (Cascoded Amplifiers)

    Homework Statement Hey guys, i can use some help with this problem: I don't really have issues with part A, its more of part B and C that i can use some help with Homework EquationsThe Attempt at a Solution
  27. synMehdi

    Antenna signal amplification

    I have an Antenna that receives signal coming from a wide band of distances, 10-2000 meters from a 10mW transmitter. I am working with 868 MHz band. What is the cheapest method ( or cheapest circuit ) to amplify this signal with an Automatic Gain Control LNA so that the received signal stays...
  28. Clear Mind

    Effects of emitter capacitor in the BJT CE amplifiers

    Suppose to have a BJT Common Emitter amplifier like the one below: Now, if we send a signal ##V_{in}## with a frequency belonging to the midband frequency interval, we can consider ##C_1, C_2,## and ##C_E## as short circuit. Questions are: 1) What is the effect of ##C_E## (excluding its role...
  29. pretty_fly

    Designing and Simulating Shaping Amplifiers for Detector Applications

    Hello everybody, nowadays I am working on shaping amlifiers and need guidiance about how to design one and do its simulations before pcb design and manufacturing. When googling about shaping amplifiers i found documents mostly about filters (active and passive), which i know works for rejecting...
  30. R

    Ultrasound NDT (non-destructive testing)

    Hi all, I've a question and I hope that I can get some answers here. As what my project has tasked, and what my lecturer had said. He needs me to build a device for NDT Testing. Currently the set up is that I would source for a transducer via olympus coupled with a USB oscilloscope capable...
  31. Runei

    Available Noise Power and Amplifiers

    Hello there, I'm working with the textbook by Wim van Etten, "Introduction to Random Signals and Noise". And right now I'm preparing for an exam in a stochastic processes course. I have a question regarding some noise calculations, that I just can't wrap my head around. I hope someone will be...
  32. T

    Anyone know anything about magnetic amplifiers?

    Hi, I was wondering if anyone knew if you could use a magnetic amplifier: http://en.wikipedia.org/wiki/File:Magnetic_amplifier.svg as like a variable resistor for controlling current from the source to the load? I imagine there would be a large voltage imposed across it when it is a high...
  33. P

    Transimpedance/Transconductance Amp: Low/High Rin & Rout, App Usage

    Why do transimpedance and transconductance amplifiers have low Rin and Rout and high Rin and Rout, respectively? Also, I am having difficulties finding applications which require the use of current amplifiers. I'd appreciate it if someone would kindly provide feedback on these three questions.
  34. A

    Need help classifying this circuit

    Hi everyone, I am trying to understand amplifiers better and had one here that I would like to build and test: http://www.ke3ij.com/amp.htm How would this amplifier be classified as? I was thinking class AB, as it has two common emitter gain stages in the beginning which serve as a pre-amp like...
  35. A

    CS amplifiers cascade problem

    Homework Statement two identical CS amplifiers connected in cascade. 1st stage fed with vsigand Rsig=100k ohm. load RL= 10k ohm connected to drain of 2nd stage. each MOSFET biased at ID = 0.25mA and VOV=0.25V. assume VA is very large. Each stage has RD=10k ohm. a) sketch equivalent circuit of...
  36. L

    Bootstrapping Amplifiers, and Signal Bypasses

    Hello, I am reading The Art of Electronics, and I have two specific questions regarding examples it has introduced. I am dealing with bipolar transistors the current chapter. I think my questions mostly stem from not understanding concepts. The text has introduced the technique of...
  37. D

    RF Small Signal Amplifiers and Cooling

    I know that in the pursuit of low noise amplifiers, the cooler the better, generally speaking. But when does it make sense to try and go through the work required to cool an amp? One of my passions is radio astronomy. I have a good collection of LNA's around of various types and an eight foot...
  38. J

    Amplifiers with Feedback: AC-Analysis and Hybrid-Pie Transistor Model

    I have attached two different amplifiers with feedback, one of them is series-series amplifier and the second one is a shunt-shunt amplifier. AC-Analysis: Using the Hybrid-Pie transistor model • Determine the amplifier parameters Rin, Ro , Mid-band gain A • Determine the low cut-off...
  39. E

    Quick question about operational amplifiers

    Homework Statement Does a noninverting operational amplifier amplify the frequency of an input, ex. a 2 kHz square wave of amplitude 100mV peak-peak, or just the voltage?
  40. P

    Operational Amplifiers - Saturation

    I am an A level physics student. I have a doubt regarding the saturation of op-amps. For a circuit with a dual power supply, each supply has an emf VS. My doubt is, why is the MAXIMUM magnitude of the output voltage VS? Shouldn't it be VS - (- VS) = 2VS? (Since the potential difference is the...
  41. C

    Photomultiplier Tube Destroying Amplifiers - Suggestions?

    Hi everyone, new poster here. I'm a chemist who's in a little over my head with an electrical engineering problem, and I'm hoping someone here might have some advice. The short version (details to follow) is that my experimental setup has a photomultiplier tube (PMT) detector whose output has...
  42. N

    Simple question on differential amplifiers

    Homework Statement My textbook says """When a dual power supply is used,the biasing resistors are so selected that the desired forward bias to the two transistors is provided,at the same time the voltages at the bases of the two transistors are brought down to ground potential. Hence when...
  43. ShreyasR

    H parameter analysis of transistor amplifiers.

    In h parameter analysis, we take the input current and output voltage as independent variables. and the Input voltage and output current are dependent on the input current and output voltage. They are related as: Vin = h11Iin + h12Vout ___(1) Iout = h21Iin + h22Vout ___(2) In case of a...
  44. C

    EE courses for designing audio amplifiers and speakers?

    Hi everyone. I've got my BS in physics, but I don't know much about electrical engineering. I've had a passing interest in do-it-yourself audio equipment for quite some time (designing and building your own speakers and amplifiers), and I've finally decided to get serious about it. So, it...
  45. 2

    Charge Amplifiers? Electric Field Mill

    I am currently working on building an electric field mill. I am in the very early stages of building this and I have little experience on the subject, unfortunately. I understand the basics and came up with a formula to calculate the current with respect to time (this is AC current)...
  46. Tesladude

    Maximizing Power Output: Amplifiers in Bridge Mode

    I read that bridge mode in amplifiers will, for example, take a 100 watt amplifier at 8ohms and turn it to a 200 watt amplifier at 4ohms. I was going to use 2 tda2050 amps, each running one speaker, but if I use 2 amps in bridge running 2 8ohm speakers in parallel, would this give me double...
  47. D

    Calculating Voltage Gain of Multistage Amplifiers

    Greetings, I want to tell me if i calculated well the following amplifications. I took several cases when the first stage is common emitter/base/collector connected to second stage with common emiiter/base/collector. Firsly i calculated the impedance of the stage 2 amplifier seen by the first...
  48. C

    Designing different amplifiers with known gain

    Homework Statement I am designing three amplifiers: 1. is an noninverting amplifier with G=200 2. is an inverting amplifier with G=-50 3. is a summing amplifier with V(out)--50V(in1)-3V(in2)-15(Vin3) all problems i(outmax)=2mA So far the only problem I have figured anything about is...
  49. G

    Electrical Engineering - Operational Amplifiers

    Hi in a homework problem I'm trying to solve circuit. I'm getting the output current of an operational amplifier going into the operational amplifier. Is this allowed? If not than I'm violating Kirchhoff Current law and my other calculated values of the circuit must be wrong. Thanks for...
  50. ElijahRockers

    Solve Op Amp Saturation: Find Rf & Output Current

    Homework Statement Va = 4V Vb = 9V Vc = 13V Vd = 8V The 220k resistor is replaced by a variable resistor Rf. What value of Rf will cause the Op Amp to saturate? Note: 0 ≤ Rf ≤ ∞ When Rf obtains that value, what will be the current flowing into the output terminal of the op amp? The...