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. 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...
  2. C

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    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...
  3. 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...
  4. 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...
  5. N

    Is a transistor a switch or an amplifier

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  6. D

    Engineering Calculating Output Voltage of an Amplifier with RC Coupling Network

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  7. S

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  8. X

    Multistage BJT Amplifier Design

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  9. B

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  10. S

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

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  11. M

    Servo amplifier to control dc motor

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  12. C

    Differential Amplifier Common Mode Problem

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  13. K

    Semiconductor Optical Amplifier Static and Dynamic Design

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  14. T

    Operational Amplifier Dependencies

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

    Summing amplifier results dont agree with theory

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  16. K

    Polarization dependace of semiconductor optical amplifier (SOA)

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  17. A

    Capacitors in Common Emitter Amplifier Circuit ?

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  18. K

    High Pass Amplifier: C & R1 in Parallel

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  19. K

    Frequency responce in a common base amplifier

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  20. wolram

    The Pseudo Radiation Energy Amplifier

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  21. M

    Troubleshooting LM386 Amplifier Noise: Capacitor Value and Behavior Explained

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  22. B

    Differential Amplifier, Single-Sided

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  23. V

    Engineering Integrator circuit using operational amplifier

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  24. K

    Design of differential amplifier

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  25. T

    Op Amp inverting amplifier , help

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  26. V

    Most of the op-amps use differential amplifier

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  27. M

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  28. A

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  29. L

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  30. S

    Voltage Gain in Midband Region of Transistor Amplifier

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  31. K

    Designing a JFET-JFET Cascode Amplifier: Tips and Resources

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  32. H

    Designing an Amplifier Circuit for Hypothermia Treatment Device

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  33. B

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

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  34. 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
  35. U

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

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  36. 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...
  37. 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!
  38. 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...
  39. W

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

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  40. D

    Need help understanding Current Draw for a Power Amplifier

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  41. 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 +...
  42. S

    The source of noise in amplifier

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  43. 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...
  44. P

    Constructing an IR Amplifier - Is it Possible?

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  45. 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...
  46. 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...
  47. B

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

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  48. S

    How Do You Design a CE Amplifier with a Gain of 10 Using a 2N3906 Transistor?

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  49. C

    Simplest amplifier design with resistor and transistor

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  50. Z

    Temperature Amplifier: Ideas & Input Requested

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