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. S

    I want to create an ultrasonic generator amplifier w/ MOSFET

    Firstly, I'm only a beginner at electronics and most of my knowledge comes from googling things. I have (several) ultrasonic transducers (100 watt 40 khz) i'd like to drive with my ultrasonic generator (100 watts 40 khz) but I'd like to up the amplitude of my transducers because I want the...
  2. EngrHdr

    Why Does My Summing Amplifier Clip Below 1 Volt?

    Hi everyone, I am trying to make a Summing Amlifier. I have simulated on computer where it is working correctly, but on real circuit it is showing some mal functioning. I am using OP 27 Op Apmp. The circuit diagram is attached. When I try to add DC voltage to AC sine wave, initially sine wave...
  3. Salvador

    Simple class A amplifier for a different reason

    Hi, so i have built some amps and power supplies before , even some real simple smps from a working circuit schematic but I have two high power npn transistors laying around and some old half baked circuit boards. I am interested can I make a real simple smps out of a 555 oscillator chip, and a...
  4. S

    Find the voltage gain, input and output resistance amplifier

    I am having a difficult time solving the question in Step 2 of the attachment. The question is "Use the equivalent-circuit model of the uA 741 to find: The voltage gain Av=vo/v1, the input resistance R1, and the output resistance Ro of the amplifier circuit. Attempt at solution: I used the...
  5. G

    Questions for common emitter, collector and base amplifier.

    Hello. I'm now studying transistor amplifier circuit and I have some confusion of definition of amplifier classification. I thought common emitter means emitter side is grounded, although there is actually some elements between emitter and ground in practice. So I thought "common" means...
  6. T

    Combine cascaded amplifier into single model

    Homework Statement 1) vs = 1 mV. Find v1, v2, v3 and vL 2) Model the three-stage cascaded amplifier by a single voltage amplifier model. What are the values of Ri , Avo, and Ro? Diagram: Homework EquationsThe Attempt at a Solution 1) v1 = 0.909 mV v2 = 9 mV v3 = 818 mV vl =...
  7. R

    In-Line Amplifier Schematics | 2 Transistor Chain

    Hello. I'm looking for the electrical schematics of this kind of in-line amplifier use behind LNB of Sat Tv to compensate coax loss. I'm mainly interested by a 2 transistor amplification chain. My request is to get idea for a personal realization totally out of tv application ...
  8. T

    How do I analyze an audio amplifier circuit?

    Hi. I'm trying to analyse an audio amplifier circuit (DC, frequency response, stability, etc.). I began with the DC bias analysis but I'm having troubles finding where to start. I've attached the full circuit and a DC simplified version. I've placed an 8 ohm resistor as the load (8 ohm...
  9. Tesladude

    Is Increasing the Power Supply Voltage in a Mosfet Amplifier an Easy Upgrade?

    I have an old mosfet amplifier which I plan to upgrade, I have never done this before but I am very experienced in electronics and have built many amplifiers before, just not mosfet amps. I am not 100% sure how the n and p channel mosfets are biased or set up but one upgrade I want to do with...
  10. Q

    MOS Amp Mismatch: Analyzing Effects & Comparing Dominance

    This is not a homework question,so please don't yell at me.. There is a question on my textbook..Analyze in a detailed manner the effects of the mismatch in the differential amplifier MOS.Which one has a dominating effect according to you and why? I know how to analyze the effects of the...
  11. D

    Car Amplifier Mod: Can It Be Used Practically?

    Hello, I am new to this site as well as to electrical theory. I recently took a second semester physics course and stumbled upon a great deal of curiosity in the electricity and magnetism portion of the class. I am taking a few courses pertaining to electricity&magnetism as well as engineering...
  12. brainbaby

    Operation of this power amplifier....

    Please help me on this... The following diagram is of a class AB power amplifier ... According to text its written that "the voltage drop across R1 and R2 should be minimum in order to produce the base current.But this minimum voltage requirement keeps the amplifier maximum peak output voltage...
  13. D

    Peak gain and IP3 of a common-emitter amplifier

    1. Homework Statement Homework Equations Hi all. Lets start with subquestion a). How do i calculate the PEAK gain? The Attempt at a Solution I drew the small signal equivalent and calculated the gain: Av=vo/vi=-gm(ro//R=1kΩ//L//C) Is that correct? How do i now calculate the peak gain...
  14. Gingerbunny82

    Analyse this amplifier for me please :)

    Hi folks, I've designed this amplifier, it uses an Ne5532p op-amp for the voltage amplification and feedback in the non-inverting configuration. The output stage is handled by two Darlington transistors, TIP 121 and TIP 126, these are hopefully biased by TIP 117 and TIP 112. I was hoping that...
  15. I

    Amplitude modulation and amplifier efficiency

    " A intelligence signal is amplified by a 80% efficient amplifier before being combined with a 12kW carrier to generate the AM signal. if it is desired to operate at 100% modulation, what is the DC input power at the modulator" The choices are a: 12kW b. 7.14kW c.7.5kW d. 15kW my solution...
  16. GGGboat

    Engineering How to Design a BJT Analog Circuit with Specific Transfer Characteristics?

    Homework Statement hello, i need to design analog circuit that has a transfer curve as seen in the following image using resistors, capacitors,voltage, and BJT (with beta value of 100). the parameters are: A=75 f1= 21Hz f2=21 KHz M1=40 M2=-20 the circuit also need to have input resistance of...
  17. R

    Finding a 1.5 GHz Line Amplifier for RG59 Coaxial Cable Loss

    Hello. I 'm looking for a line amplifier schematics working around 1.5 GHz to compensate coaxial ( RG59/CU) loss behind a L.N.A
  18. tendo

    Strong static magnetic field influences on IC

    Does anyone have any papers or materials on how strong static magnetic field (7 to 12 Tesla) influence BJT and MOSFETS? I didn't find many people doing research on this. All I find is some experiment results. It seems transistor parameters change a lot with different azimuth angle due to Hall...
  19. R

    Engineering Where is the bandpass filter in this circuit?

    Homework Statement I am doing a project on the Elenco AM/FM superheterodyne radio kit. I have been stuck for ages trying to figure out how the two common emitter amplifiers are tuned to filter out anything that is not around 455 kHz. I tried to find a bandpass filter, or a high-pass and a...
  20. Rob1818

    BJT Collector to Emitter voltage

    I have been checking the BJTs on a car audio amplifier board with my DMM's diode test feature, and I need a little help understanding something I have been noticing: The base to emitter and base to collector voltage drops are present, and show an open circuit when the leads are reversed as they...
  21. beyondlight

    Calculate gain for differential amplifier

    Homework Statement Calculate gain (u_o/u_i) for a differential amplifier with symmetric output. Both transistors have the same transconductance gm. Transistor output resistance r_0 is neglected here. circuit: http://sv.tinypic.com/view.php?pic=14cea8p&s=8#.VSf7Evl_vxM Homework Equations...
  22. S

    Amplifier Circuit Advice -- AF/RF

    Not sure if this is the right place to post, but here we go, my first question: I've been searching around for a simple circuit for amplifying rf at around 7MHz, and went ahead and followed this guide, 2nd picture down, and built the amplifier. It works, even with some small resistor value...
  23. A

    Finding the Frequency and Critical Value of a Feedback Amplifier

    Homework Statement Consider a feedback amplifier for which the open loop gain A(s) is given by: A(s) = X/ [(1+s/Y)*(1+s/Z)2] |s=jω Where X = 7500, Y = 90000, and Z = 800000 a) If the feedback factor is independent of frequency, find the frequency at which the phase shift is 180°. b) Find the...
  24. Togomori

    Discrete class D amplifier outputs low volume

    Hello everyone, I have a discrete class D project that I need help with but since I'm not an analog guy I got a problem. So far I got everything set up and the discrete class D works perfectly. But only at maximum of 6 volts otherwise the Transistor M3 gets really hot and burned, how do I solve...
  25. CKaiL

    Single stage amplifier with current mirror biasing

    Homework Statement Homework Equations ID= kn (Vgs - Vth)^2 The Attempt at a Solution I asked to find the current I D , M2. [/B] I think in order to solve this question I need to find Vgs but how do I do that? RC1 = 2k ohm R = VDD - Vgs / I D ,M2 VDD = 5V , and R = 2k ohm and I have 2...
  26. STEMucator

    BJT Amplifier Analysis: Questions and Solutions

    Homework Statement Homework EquationsThe Attempt at a Solution I was not too sure about the analysis and thought I would ask some questions. Do I short out the AC source ##v_i## when doing the DC analysis? The input capacitor with ##C = \infty## is designed to couple the AC signal and...
  27. L

    Transistor as an amplifier (doubt)

    The npn transistor is said to function as an amplifier only in its active state (emitter base is forward biased and collector base is reverse biased). It is considered that majority of the electrons reaching the base layer is dragged into the collector layer. So the emitter current (ec) is...
  28. A

    Common emitter amplifier Electronics

    Rb=40 ohms RL=100 ohms Vcc=15V I need help in figuring this problem out, I understand if anyone here doesn't want to give me the answer but I would appreciate if someone would give me a formula in which I could solve the problem myself.
  29. Machinekraft

    What Are the Limits of Torque Amplification in Mechanical Torque Multipliers?

    What is the maximum torque amplification that can be achieved using a mechanical torque amplifier?
  30. B

    Create a two-stage amplifier without feedback

    < Mentor Note -- thread moved to HH from the technical engineering forums, so no HH Template is shown > Hi, I have a task to create a two-stage amplifier without feedback. It shall be made with these requirements; It shall be connected to a source of internal resistance equal 2.2kΩ and a...
  31. Rampart

    How to Find Ibq and Vceq in a Common Base Amplifier?

    Homework Statement In the following common base circuit,β=100.If Vcc=15V, VEE=4V,RE=3.3KΩ, Rc=7,1KΩ find the Ibq and Vceq(they are related to the dc values of the Q point) Homework EquationsThe Attempt at a Solution Well ah...i mainly want to ask some things.However knowing that i must...
  32. STEMucator

    Design Amplifier w/ 1k & 10k Resistors for +10 V/V Gain

    Homework Statement Given the availability of resistors of value 1 kΩ and 10 kΩ only, design a circuit based on the non-inverting configuration to realize a gain of +10 V/V.Homework EquationsThe Attempt at a Solution So I was doing some of those good old design problems, and I came across this...
  33. S

    Can a Lock-in Amplifier Handle -30dB SNR?

    Hi, I wrote a simulation of lock in amplifier using Matlab and now i want to test it for different SNR. I added to the signal white gaussian noise. In all the spec that i read, always written that the lock in amplifier can handle -100dB of noise. When I add a noise of SNR=-30dB the lock in...
  34. Paradoxs

    Biomedical Engineering - Amplifier

    Homework Statement I- What is application of this circuit? What does it do? II- Simulate this circuit in a simulator software and by determine correct values for resistors, show heat losses (H) is nearly constant. III- Calculate H analytically (manually) (voltage division) and compare with...
  35. M

    How to Design a Simple Transistor Amplifier with Given Data?

    Homework Statement The circuit above shows a simple transistor amplifier with the given data: β=100, VA = 100V, RL = 10kΩ a) neglect the "early-effect" and design the circuit so that IE = 0.5mA and VC = 5V. Homework EquationsThe Attempt at a Solution I'm familiar with the β part, it means...
  36. A

    Building a Speaker with a Class AB Amplifier

    Hello, For a school project I need to build a simple but working speaker. I am currently stuck on explaining how the signal amplifier works. Here is a schematic of an AB amplifier from Wikipedia. I have add a positive and negative sign indicating the connection of the battery. It contains 2...
  37. T

    Crystal oscillator and amplifier purchase

    in my previous thread i was trying to build a sine oscillator and an amplifier. decided to give up on the idea and purchase. any chips out there that can give me 30-40volts peak to peak. the frequency is not an issue as long as it is above 1 MHz. i guess i can use any crystal oscillator as long...
  38. M

    Help needed with charge sensitive amplifier circuit

    hello sir, we are designing radiation measurement readout front-end electronics, as part of our project ,in very 1st step to understand working of CSPA(charge amplifier) i had done little experiment by connecting photodiode with opa657 .here i have used general purpose ir photodiode and Rf=147k...
  39. ranju

    Output Voltage of Feedback Amplifier is 14.85V

    Homework Statement An amplifier without feedback provides an output signal of 15 V with 10% second harmonic distortions when input signal signal is 15 mV. If 1.5% of the output is feedback to the input in a negative series shunt amplifier, what is output voltage?[/B] Homework Equations input...
  40. M

    Clipping in a transistor amplifier

    I need to understand how does an amplified signal gets clipped depending upon the biasing voltage level? It says that upon insufficient biasing, the output voltage becomes constant, but how? Please if you attach this link:- http://www.electronics-tutorials.ws/amplifier/amp_4.html I mention you...
  41. F

    Linear Inverting Amplifier Help

    Homework Statement A linear inverting amplifier has these characteristics: -5.0V < vo < +5.0V Av=35 dB The output rails at -5.0V and +5.0V That is, the amplifier outputs no voltage larger in magnitude than 5.0V. What is the gain in V/V? What is the output if vi=-8.0V? Homework...
  42. BeautifulLight

    How is the grid biased on a triode vacuum tube amplifier?

    Here is my single triode vacuum tube amplifier circuit I understand there needs to be a bias on the grid otherwise the signal will be rectified -not amplified. Is biasing the grid as simple as running a resistor in-between the grid and the cathode on the power supply like this (in red)...
  43. N

    What's the deal with the power section in my Adcom amp?

    It's been over 20 years since I received an electronics degree I never utilized. Hopefully you guys can help jog my memory a bit as I really want to start getting back up to speed. I've now taken on a more aggressive project, other than soldering pre-made boards, to help lubricate my old...
  44. Tesladude

    Why Is My Boss Subwoofer Amplifier Distorting at High Volume?

    I have a boss subwoofer amplifier which I recently discovered was causeing the distortion I have been hearing in my car. this amplifier consists of a PWM powersupply turning the 13.5v from my on car to a +45 -45 power supply. Then there are 8 mosfet transistors, 4 in parralel powering one...
  45. Tesladude

    Help -- car stereo is acting up with hand made amplifier

    I am adding 2 extra rear speakers in my jeep, I have some rca cables comming from the rear speaker pre-amp outputs from the back of my pioneer stereo. My plan which works beutifully is a dc-dc boost module bringing the cars 12v up to 20 for the main amplifier. The main amp is a 2x25...
  46. E

    How Do Current Sources Affect CMRR in Differential Amplifiers?

    Hi! Here is my task: Current sources Iss which are used for differential amplifier in photo c) are shown in photos a) and b). DC voltages VB1 and VB2 provide saturation for all MOSFETS. Calculate ratio of CMRR of differential amplifier with current source from image a) and CMRR of differential...
  47. E

    MOSFET differential amplifier gain

    Hi! Here is my task: For differential amplifier on scheme calculate voltage gains Av1=vout1/(vin1-vin2) and Av2=vout2/(vin1-vin2). MOSFET's M1 and M2 have same characteristics. MOFSTE's M3 and M4 have same characteristics. All MOSFET's are in saturation. Assume that gm*rds>>1. How to use fact...
  48. E

    MOSFET amplifier input resistance

    Hi! My task is to calculate input resistance for circuit below: VDD=10V, Vtn=1V, β=1mA/V^2, VA=100V, load resistance RL=20k. Here is model for AC analysis (DC source and infinite capacitances are short circuits, current directions chosen arbitrarily): After calculationg input current iin...
  49. E

    BJT amplifier - calculate resistances

    Hi! Here is my task: Calculate RC1, RC2, RE2 for maximum undistorted symmetrical signal at output if DC collector currents are IC1=IC2=1mA. Calculate voltage gain Av. Vcc=9V, RE1=1.8kΩ , VBE=0.7V, VCES=0.2V, VT=26mV, beta=100, VA→∞. Solution: RE2=700Ω, RC1=5.724kΩ, RC2=3.141kΩ...
  50. P

    Output voltage of differential amplifier

    Homework Statement Find output voltage of differential amplifier having differential gain of 100 and common mode gain 0.1 if input voltages are v1=2+0.55sinwt and v2=0.5-0.005sinwt Homework Equations The Attempt at a Solution well, from sedra smith book i found the formula for...
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