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. H

    Solving Common Base Amplifier Problems: Homework Statement & Solutions

    Homework Statement The problem statement, given solutions, and my small signal drawing are attached Homework Equations Rout, Rin, Av The Attempt at a Solution To begin with, our text seems to alternate between using approximate equations and exact derived equations without stating...
  2. A

    Finding Feedback Polarity - Step By Step Guide

    Homework Statement I have to find the feedback polarity. I proceeded as follows : Homework Equations The Attempt at a Solution 1. As Iin = iF , increasing Iin will increase iF 2. Now drain current for MF is increasing so Vgs of the transistor should increase 3. That means...
  3. Tesladude

    Amplifier Circuitry w/ LM4780 IC: Adjust Output w/ Potentiometer?

    I am making an amplifier with 2 lm4780 ic The gain is set by a resistor between the output and negative,I want to use a potenciometer to be able to adjust this, so my question is: will lowering the ohms lower the output or will increase the output or what?
  4. D

    Solve Multistage Amplifier Homework | Av=Av1*Av2

    Homework Statement I want to solve the circuit using the formula Av=Av1*Av2 where Av1 and Av2 are the gains(volts) of the 2 stages and i have some questions. V2 is equal with -(βIb1+Ib2)*R3=(β+1)Ib2*R5+Ib2*rbe2 Now when i calculate Av1 and Av2 i take each stage separately from circuit (example...
  5. J

    Question on Non-Inverting Amplifier

    Homework Statement Consider the circuit that attaches in the attachment. Calculate the Vout. Homework Equations Non-inverting om amp: Gain = Vout/Vin = 1 + (Rf+Rs) Golden Rules: i- = i+ =0 V- = V+ The Attempt at a Solution Gain = Vout/Vin = 1 + (Rf+Rs)...
  6. H

    CE BJT Amplifier - Collector Resistance

    We are studying single transistor amplifiers, and in the text where the collector resistance of the CE amplifier, Ric, is derived, the final equation is Ric = ro[1+gm(Re||r∏)] (approximation) This equation is highlighted and emphasized as something we should remember, then shown again in...
  7. T

    Difference between Difference and Differential Amplifier

    Can anybody please explain the difference between difference and differential amplifier as both looks same and its confusing? Reagrds
  8. P

    Common base amplifier voltage gain

    Hi, I have a common base amplifier circuit but I am not sure of the equation to use to calculate the voltage gain? Could someone help me please
  9. F

    Sensitivity of lock-in amplifier

    Hey I have a quick question whose answer is well-hidden on google since the key word of the search attempts is sensitivity, which of course returns results about phase-sensitive detection, and seemingly phase-sensitive detection only... My question is what the exact definition of the...
  10. S

    CE amplifier - How to limit bandwidth?

    When using the CE BJT amplifier configuration, when a shunt capacitor is placed across the collector resistor, how does this act as a bandwidth limiting cap?
  11. G

    Electrical Circuit Question - Integrating Amplifier

    Homework Statement http://img801.imageshack.us/img801/4227/capturebsw.png Homework Equations The Attempt at a Solution Alright I'm not really sure how to solve this problem. I have redrawn the circuit below without the operational amplifier. In ideal operation amplifiers there's no...
  12. W

    Recovering WWII magnetic amplifier technology

    I have a continuing interest in recovering the schematic of a 2 stage DC magnetic amplifier that was used in my graduate school. I was in the physics lab at the University of New Orleans working with superconductors. The magnetic amplifier was used to provide feedback from a rotating...
  13. S

    What are some recommended opamps for audio applications?

    I am having trouble figuring out how to design multistage amplifiers in general. I am working on a project in which I take the small signal from a condenser mic ( ± 5mV ), amplify and filter it a sufficient amount such that I can read into a microcontroller and process the information. I would...
  14. L

    How does the source voltage affect the inductance in a 1 Mhz amplifier circuit?

    Hi, I am a inventor and Electronics Tech. I am creating a 1 Mhz Amp for my own invention, and it will be enclosed in a Faraday cage so there is no emissions to worry about. I have been reading Fundamentals of Engineering Electromagnetics, and was wondering about the difference in the source...
  15. A

    Finding V(out) of Operational Amplifier

    Homework Statement Op Amp powered from +-20V DC. Find V(out) in Volts. All Resistances/Batteries given. http://imageshack.us/a/img805/2803/photoup.png Help would be much appreciated
  16. C

    Power of Burst waveform going through an amplifier

    Hi all, How would I calculate theoretical power of: 1Vpp 1Mhz (sinewave) 200 cycles 100ms interval 50Ω load This waveform is going into a 55db amplifier. Any help would be great. Thanks, Mark
  17. K

    Sketch the relationship of a VCVS amplifier

    Homework Statement "Sketch the V_o vs V_i relationship for a voltage controlled voltage source amplifier" Homework Equations none really The Attempt at a Solution Ok, so I understand and know by heart the ideal and the practical relationships for a (respectively) ideal and...
  18. R

    Need help with transconductance operational amplifier

    Hi all, Does anyone know how do I connect an OTA if I want to use it as a voltage-controlled current source, meaning that it will ouput an AC current when i supplied an AC voltage? Any guide I can refer to? And how do I adjust the gain or transconductance, gm? For example, OPA860 with...
  19. W

    Can you explain this amplifier circuit to me?

    I just want to know what you think (in order of when you think it) when you look at this circuit. I'll post what I think. 1) without input: Current goes through R1 and TR1 which allows more current to flow through R3, R4, C2 and R5 and to TR2. The current through TR2 inhibits the current...
  20. A

    How Does Input Resistance Affect Op Amp Performance?

    I have an un ideal OA aplifier(Amax=-9.975). I have to evaluate its Rinput--> it has to be something like 10*10^10 Ω I need to put a potenciometr after Vin and to "play" with it when I get half of Vout/vin. when do I need to put it? and what is my voltage equations? thanks.
  21. Hysteria X

    How does a transistor work as a switch and amplifier?

    How does a transistor work as a switch and amplifier?? i know a transistor is a device that controls the flow of current but how does it act as a switch and an amplifier? i tried reading about it on so many places but i just can't seem to get it :confused: ...the diagrams just don't make sense...
  22. E

    Looking for Books on Amplifiers and OP-AMPs?

    Hi :smile: i want some books about amplifier by transistor and... OP-AMPand thank you
  23. Runei

    Where Can I Find Analytical Resources for Class D Amplifiers?

    Does anyone know a good book about Class D amplifiers, or perhaps some other resources? I'm looking for a place where they have a good analytical approach. Equations and stuff, and explanations thereof. Any takers?
  24. xortan

    Design a MOS Voltage Amplifier with Gain of 50 V/V

    Homework Statement I need to design a MOS voltage amplifier with a gain of 50. Homework Equations tox = 5 nm u = 500 cm2/V-s Cox = 6.903 mF/m λ = 0.1 Vdd = 2.5V The Attempt at a Solution I am getting confused on just about everything... I am to design a voltage amplifier...
  25. D

    Selecting Vgs and Vds for MOSFET Amplifier

    Hello All, I just finished a college course on electronic circuits (opamps, mosfets, bjts, etc) and I'm trying to put some of that knowledge towards designing a basic MOSFET amplifier circuit. Right now I'm at the stage of selecting DC biasing points and I'm having a bit of difficulty...
  26. M

    Instrument amplifier or just operational amplifier?

    Hi: i have a project to design ECG system: read ECG signal by using (DAQ)data aquestion and the Signal processing(bandpass& notch filter) will be done by using MATLAB program. I was Intended to use instrument amplifier to obtain I,II or III signals as this figure: but my supervisor...
  27. G

    Why Am I Misunderstanding the Output Resistance in This Circuit Analysis?

    Output resistance problem Homework Statement Hi, I am not getting the answers right, and I think I misunderstand the logic behind this circuit. http://imageshack.us/photo/my-images/577/screenshotfvm.png/ Homework Equations I know that the equation of Vin is Vin=(VsRin)/(Rs+Rin) and...
  28. Q

    Which resistors should I use to generate a gain of 15 on an inverting amplifier?

    I have the set of values for resistors available: 10-12-15-18-22-27-33-39-47-56-68-82 And I need to get a gain of 15, which values should I use to get this? Also, I have a non-inverting amplifier, and again, I need a gain of 15. I selected the values: R2=12 and R1= 68+82+18=168 I assumed I was...
  29. J

    Trying to replicate an accelerator pedal using a differential amplifier

    I'm trying to replicate the voltages coming from an accelerator pedal, to the ECM, on 6.0 L Diesel engine. I acquired the three separate voltages using an oscilloscope. I have access to two analog output channels on the dyno. Out of the three voltages two them follow each other by a...
  30. B

    Differential amplifier with current mirror load

    The question and my attempt have been provided in the attachments...my problem is trying to find the differential gain, i have worked through to an answer but the answer I'm getting doesn't seem correct...also i have absolutely no idea how to derive the common-mode gain...any help is much...
  31. S

    Transfer function of Instrumentation amplifier with DC suppression filter

    Homework Statement I want to find the overall transfer function of Instrumentation amplifier with a DC-Suppression filter. I know how to calculate the TF of a normal Instrumentation amplifier. But when feedback is given from the Filter to the IA, I couldn't find it. Homework Equations...
  32. W

    Search for magnetic amplifier circuit

    I had the pleasure of using and seeing the schematic of a two stage magnetic amplifier that was used to control the magnetic field of a large electromagnet, during my graduate work in superconductivity at the University of New Orleans. It had a large DC gain and with a resistor for feedback...
  33. S

    Will i need amplifier in this case?

    Hi: i have ADC(analog to digital) has a resolution 12 bits and the input range is from +50mV to -50mV, this men the precision is about 24uV i want to use this ADC for a signal has Vp.p from 0.7mV to 1mV so can i use this ADC directly?or i must use amplifier ??
  34. M

    Please help transistor amplifier

    can somebody teach mm how to find desired voltage gain of ce a transistor amplifier which is formula, i know the formula is rc:rl/re but i want for example a voltage gain of 50 for example input desired data: desired voltage gain 2.0 which i want to know f_min = 10 HZ z_in = 50 K...
  35. L

    Troubleshooting Audio Amplifiers: Dealing with a Faulty Capacitor (C2)

    Hello people I am doing an audio amplifier, but I am really stuck in the circuit because the 1uF capacitor (C2 )doesnt work properly next the the potentiometer , but if I took off the Capacitor C2 I can hear music through my speakers, but with really bad quality. I don't know what you can...
  36. R

    OP amp: Find Vout of this amplifier

    Homework Statement Find V_{out} of this amplifier Homework Equations V_{out}=G_v(V_{in}+V_F)=G_v(V_{in}+B_vV_{out}) The Attempt at a Solution I have been stuck on this for a week. I really don't know where to start. Have read the chapter multiple times, tried to create it on...
  37. M

    Inverting Amplifier maximum output voltage

    Homework Statement I'm doing a physics lab that involves an inverting amplifier. I'm pretty crap when it comes to electronics. I've discovered that the output voltage won't go past 8Vrms. The amplifier is like the one here...
  38. C

    Common-Source JFET Amplifier problem

    Homework Statement For the prelab assume that the JFET has the following typical specifications: IDSS = 10.0 mA VGS(OFF) = -3.5 V rds = 50.0 kW 1. Complete the design for the bias circuit in Figure 1 given that the desired Q-point for the JFET is ID = 2.0 mA and VDS = 6.0 V by following these...
  39. E

    Calculating Gain of a Multistage Amplifier

    Homework Statement for the circuit shown , if i want to calculate gain of the second stage then do i need to consider the output resistance of first stage as the source resistance for the second stage ? Homework Equations The Attempt at a Solution first stage is common collector...
  40. J

    Are There Ready-Made Amplifier Modules for 50A 50mV Current Shunts?

    Hello All, I'm designing a test setup that requires the use of a 50A 50mV current shunt to take measurements for a circuit which produces pulsed DC currents up to about 100 kHz or so (highest frequency component anyway). I would like to use this shunt here, but also amplify the signal 10x or...
  41. E

    Common Emitter Amplifier Design

    Homework Statement I have to design a Common Emitter Amplifier using a 2N2222 NPN transistor and an 18V DC supply. The specifications are as follows: Should be stable for variations in forward current gain, β. The input signal to the amplifier is a 0.2 Vp sinusoidal signal, at a frequency of...
  42. E

    Audio Amplifier Design Basics: Problem & Solution

    I am studying basics of analog circuit design from microelectronics circuit analysis by donald neamen And in that i encountered a problem in design of audio amplifier. The question and solution is given in the attachment. And i want to know that in the output emitter follower why there are no...
  43. K

    Source Follower Large Signal - MOSFET amplifier

    I'm still not very confident in analyzing circuits. Here's what I know: 1) v_o=v_IN - v_T 2) id=k/2*(v_IN-v_T)^2 3) v_o=v_S-(k/2)(v_IN-v_T)^2*RS 4) v_o = v_S-id*Rs iDS = v_o/RS The answer I chose in the photo was based off of other online discussions. I'm very confused and don't have the...
  44. E

    BJT differential amplifier, small signal analysis

    Hello, I'm having some issues with small-signal analysis of BJT differential amplifiers. Let's say I have this BJT differential pair and suppose that Q1 and Q2 perfectly match: http://i50.tinypic.com/14ahdgn.jpg Suppose a small differential input is applied and consider the small–signal...
  45. J

    How to find the input resistance of an amplifier?

    Homework Statement Here is a picture of the problem http://i1226.photobucket.com/albums/ee410/jean28x/37A91AE5-904B-45C1-8A04-C5855FF971D8-87001-000004D91E955189.jpg Homework Equations Im guessing Vo = Avo VL (RL/(RL + Ro)) The Attempt at a Solution The solution is...
  46. H

    Can someone resolve an argument over audio amplifier and wiring theory?

    Hey, I'm sorry to bother you guys but I got a quick question I was hoping you guys could answer. I was just hoping someone had a definitive explination as to why a $500 audio amplifier that can put out 200 watts per channel will sound exactly the same as a $10,000 amplifier putting out 200 watts...
  47. R

    Personal Voice Amplifier Background Hum Trouble

    Long-time lurker, first post, here goes. So I'm working on a personal voice amplifier for a face mask. I have the dynamic mic element ("www.accusonicproducts.com/pdf/G01A009-PFK.pdf2FVVVHLD_Q" ), which feeds into a 3v class A preamp, through a 100k audio taper pot, to a 6v lm386 amp with the...
  48. A

    Designing a Lock-in amplifier from zero

    Hello everyone I have completed my freshman year in EE. For the summer, my professor has asked me to design a lock-in amplifier. First he has asked me to read about AD630. Now after reading the datasheet at (http://www.analog.com/static/imported-files/data_sheets/AD630.pdf), I was a bit...
  49. Topher925

    Lock-in amplifier driving me crazy

    I have a project where I'm measuring the phase of a signal compared to a signal reference using an SR830 lock-in amplifier. My problem is that the amplitude of the input signal periodically changes over time and this is causing a false measurement in the phase of the input signal. I can't figure...
  50. M

    Engineering Design Op Amp Circuit: Low-Pass Filter to G(s)=10/(s+10)

    Homework Statement Design an op amp circuit that acts as low-pass filter with the following transfer function G(s) = 10/(s +10)Homework Equations Inverting operational amplifier Vo(s)/Vi(s) = Z2(s)/Z1(s) Non-inverting operational amplifier Vo(s)/Vi(s) = Z1(s) + Z2(s)/ Z1(s) The Attempt at a...
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