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Questions tagged [amplifier]

An amplifier can be used to adapt the range of the signal to a requirement, to make it more robust for transmission, or to satisfy interface requirement (like input/output impedance)

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Capacitor in parallel with resistor on xoscope amplifier schematic

Short version: Why is C3 necessary in this circuit? Explanation: The schematic for the input buffer/amplifier circuit for xoscope is made up of subsections that are mostly broken down in the ...
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3answers
3k views

Question about the output voltage of an op-amp. (ua741)

When i hook up my opamp to a 9 volt battery (like in the image below), i get 8 volts from the output pin. It gives the same reading when i attach both the inverting and non-inverting pins to the 9 ...
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2answers
2k views

Noise when powering headphones amplifier through USB port

This question is actually connected with this one: Getting 1.2V from USB I've successfully connected my FIIO E3 headphones amplifier to USB (so that I don't have to use batteries). But I've notices ...
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1answer
553 views

What type of amplifier do I need for this project?

I'm trying to make a custom PA system for my car, but I am confused about what type of amplifier I might need, or do I need one at all? I'm wanting to take the main sound unit out of a "personal ...
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1answer
348 views

Adding microphone/amplifier to Gumstix Overo Earth COM?

I am new to hardware hacking in general. I have a Gumsitx Overo Earth COM and a Palo35 expansion board with audio in/audio out capabilities. According to Gumstix's wikipage on audio input, the ...
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2answers
1k views

What's a reference text on analog design?

I'm looking for a intermediate text that covers (discrete) amplifier circuit theory using BJTs and FETs and circuit elements such as current mirrors, differential stages, feedback theory, etc. My ...
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1answer
1k views

How to measure battery voltage

I am building a battery powered device. Almost all of my logic is running at 3.3v, although I do have a 5v supply for a few hobby servos. I want to measure the battery voltage, but I can't do so ...
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2answers
2k views

mute de-amplify sound volume

I want to de-amplify the sound volume of my television. My native language is not english, and I do not know the correct word, if any, for the opposite of amplify. When my TV is turned from volume ...
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2answers
2k views

How can I attenuate any signal to 5V peak-peak?

How can I attenuate any signal to 5V peak to peak? I tried the following design : While I limited the output to 5V peak-peak, the circuit clipped the output to 5V instead of attenuating it. My ...
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2answers
211 views

3.5DB splitter loss in voltage?

I am trying to figure out the loss from a cable splitter. I am assuming it is analyzing any other filter circuit. This should equals a loss by a factor of 1.5 or is there some special nomenclature for ...
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2answers
1k views

npn transistor base current question

Hi i am new to using transistors for signal amplification. Can someone explain to me how to figure out the amount of current being drawn into the base of the transistor when it is in the common ...
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2answers
691 views

Circuit to exaggerate differences in current

Basically what I am after is some sort of a circuit which will amplify higher voltage signals, but possibly dampen lower voltage signals, in order to make a wider separation between high and low ...
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1answer
587 views

Circuit diagram and components for Comfortron controller (Chevy, Oldsmobile, …)

I am trying to help repair a Comfortron heating and cooling controller for a late 1960's Chevrolet Impala. The Comfortron is an early climate control system that uses a combined vacuum and electrical ...
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5answers
4k views

Differential amplifier - what is the differences between CMRR and CMR?

I know that CMRR is Common-Mode Rejection Ratio, but what is CMR? $$CMRR = \dfrac{A_{dm}}{A_{CM}}$$ I didn't find any mention of it in Sedra & Smith bible. Does anyone know what CMR is?
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1answer
261 views

What is the best way to remove the non-rejected portion of a common-mode voltage and any bias voltages from a differential voltage measurement?

I am using a high-common mode differential amplifier (AD629) to measure several DC 10 to 15 voltages stacked together. Since the AD629 is not the cheapest amplifier in the world (though not as ...
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3answers
1k views

LM386 output signal problem

I've built a signal generator (with an Arduino) what can output 18kHz and 19kHz signals (separately) and it's connected to a speaker. This works just fine, there are no signals on awkward frequencies. ...
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2answers
517 views

Theoretical analysis of amplifier circuit

I have the circuit of the amplifier below. I want make the DC analysis and find the gain the amplifier produces and the cutoff freq(high-low). My problem is that it's been 15 years since I was ...
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2answers
34k views

Difference between cascade and cascode?

What is the difference between cascode amplifier configuration and cascade amplifier configuration?
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2answers
5k views

Amplifying and filtering a very low frequency signal(Bandwidth of 4Hz)

Good night, everyone. I want to amplify and filter a signal that has a bandwidth of 3.5Hz and is of the order of 5 - 40 milliVolts. I plan to amplify the signal before filtering it so as to prevent ...
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3answers
2k views

Does this amplifier work with 5V?

I'm using an Arduino to read an analog signal from an electret microphone. Here is the circuit: But I will be powering it with 5V from the Arduino, So would this work okay? Thanks!
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3answers
6k views

Audio Amplifier PCB Design Tips

I am going to design a stereo audio amplifier with TDA2030A. This is going to be an amplifier that is going to be powered from 27.6V DC and 12W per channel. Is there any sources that I can learn PCB ...
2
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4answers
2k views

Sub-Miniature version of the 12AU7 valve (vacuum tube)

I want to make my own valve amplifier, and for that, I'll be using an 12AU7 dual triode tube. Since the 12AU7 is quite large, is there a sub-miniature version available? Also: the main difference ...
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1answer
2k views

Capacitor current leakage measurement using transimpedance amplifier

I was reading a text about measuring capacitor's current leakage using a transimpedance amplifier circuit as the author says this is a rather cheap and reliable to measure currnt leakage, I was ...
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4answers
11k views

Intrinsic Gain vs. Voltage Gain

I was wondering what the difference is between intrinsic gain and just "normal" voltage gain of a circuit i.e Vout/Vin?
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2answers
1k views

How can I actuate a relay coil from a headphone jack's internal SPDT?

I want to plug my iPod which in turn supplies power to an external audio amp while sending iPod audio signal to same amp. Is it possible to wire an 1/8" (3.5mm, mini) stereo jack in such a way that ...
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1answer
1k views

Calculating gain of Amplifiers

I have read an interesting formula that says that \$\mbox{Gain of an amplifier} = \dfrac{\mbox{resistance connected at the output}}{\mbox{total resistance between source and gate of the amplifier}}\$...
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1answer
1k views

Video signal attenuation

Which is the best way to attenuate a video signal? I need to reduce the Vpp (Peak-to-Peak Voltage) from 2V of a PAL video signal to 0.75V. I am familiar with filters and amplifiers (like Op-Amp ...
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3answers
2k views

HUGE capacitor recommended in datasheet for Audio Amp

I'm using the TPA3111 audio amplifier in a circuit of mine and I'm working on adding the appropriate capacitors. However, on page 18/19 of the datasheet TI recommends to use a 220mF capacitor on the ...
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3answers
785 views

Part for VHF/FM booster?

I'm needing to create a booster and the easiest schematic I've found is this: http://electronics-diy.com/500mW_FM_VHF_Transmitter_Amplifier_Booster.php however, they do not document what part they use ...
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2answers
4k views

Whatever happened to Tripath?

Tripath made some clever digital amplifier ICs in "class-T" as they called it. Seemed to have a better performance than class-D at a comparable price. Went bankrupt in 2007, but I think this had more ...
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3answers
3k views

Picking a DAC for an audio amplfier

I'm trying to use a specific audio amplifier, TPA3111D1, to power a 10 watt speaker from a microcontroller. I would like to generate sound from a microcontroller that doesn't have a built in DAC, so ...
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2answers
4k views

Input sound to arduino via microphone jack

I'm designing a gadget which will light up LEDs using a microcontroller. I'd like for it to respond to an audio signal, so I was thinking there are a lot of ways I could do it: If I can accurately ...
3
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1answer
364 views

DAC and/or output amplifier selection for a MP3 player?

I am designing my own MP3 player now. While decoding & all digital backend looks straightforward, I am only puzzled with audio output (i.e. DAC->Amplifier part). My goals are 1: sound quality 2: ...
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3answers
2k views

Analogue automatic gain control

I have to amplify a microphone signal to be in the range -2.5 to +2.5V. It is currently providing a signal that has a peak amplitudes of around 2V. This, however, is highly dependent on the situation (...
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1answer
2k views

Unexpected results with TDA 7052

I built the TDA 7052 circuit from the datasheet and connected it to my computer's sound card and a 50 \$\Omega\$ speaker. Here's the circuit: The \$R_s\$ is the source impedance, which I can't ...
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2answers
1k views

Operation Amplifier with Transistor output

Is there a name for feedback amplifier topologies which include an opamp and transistor in the feed-forward path?. I need to design an amplifier with high bandwidth (almost 100 MHz) and high gain (50) ...
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2answers
178 views

Amplifier power draw

I'm working on a project where I'm going to drive 2 x 8-ohm loudspeakers using 1 (or more) car batteries and a Class-D amplifier. The setup is going to be used at a festival, so I need maximum ...
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4answers
1k views

How to implement SRAM sense amplifier?

I am designing a simple programmable LED screen system as an exercise, and I need a non-standard type of SRAM (16x5) so I am designing the memory circuits. I have looked everywhere (Digikey, TI, ...
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1answer
2k views

Can I replace LM358N with NE5532N dual op amp?

In this circuit LM358N 1MHz 32V dual op amp is used (+12V and -12V). The question is, can I simply replace it with NE5532N 10MHz +-22V dual op amp for up to 8MHz DDS signal source? Basically, this ...
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3answers
1k views

Solving DC Operating Point of Common Source Amp

My lab partner and I are really stumped. We are given a circuit that has a FET with a \$V_{DD} = -V_{SS} = 15\mbox{ }V\$. We are told \$A_V = 20\$ and \$I_{DS} = 1\mbox{ }mA\$. The DC circuit is ...
3
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1answer
215 views

How can I protect the amplifier behind a headphone jack when interfacing with external circuitry?

I am wanting to mess with the output of my guitar amp. Not actually opening it up, just taking the headphone-output and connecting it to a breadboard and such. What form of protection, if any, ...
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3answers
1k views

Simple Adaptive Amplifier Options for Sensor Interfaces

Related: High Resolution ADC for Noisy Sensors in Variable Conditions I'm building an interface using resistive textile-based sensors that may have different resistance ranges depending on ...
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10answers
16k views

LM394 is obsolete. What is the new standard log amp circuit?

The traditional logarithmic amplifier circuit is described in National Appnote 311: This circuit uses the difference of two transistor currents to generate the log of the input over a pretty wide ...
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2answers
7k views

Amplifying sound from a microphone

I have a small piezoelectric ultrasonic microphone (receiving signals of around 40 kHz). But the voltages it generates are too small to be read by my micro-controller's ADC. So I want to amplify the ...
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2answers
6k views

Short circuit protecting a class AB amplifier

I am designing a little class AB amplifier for a small circuit. This circuit is biased such that it has low crossover distortion. Below is a schematic: As you can see, I have inserted 68 ohm ...
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1answer
1k views

Testing an Audio Power Amp with Paralleled Transistors

A question concerning my current repair project of an audio amp that uses big (600 W) but otherwise rather classic complementary output stages: I assume when testing an audio power amp with 6 pairs ...
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3answers
1k views

Choosing output filter inductors for switching power amplifiers

Class D PWM switching power amplifiers use an LC filter at the output to filter out the switching harmonics: Other than the inductance value, what properties are important for this inductor? What ...
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2answers
178 views

Does socket orientation have an effect on sound?

Is it possible that the socket orientation (in Europe: one pin 230V, the other ground) can have an effect (albeit very small) on the amplifier behavior of a very old stereo sound system? What is, if ...
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2answers
537 views

Smallest audio amplifier?

At the moment I'm using an amplifier based around a NPN transistor and some resistors. Its configuration is as an emitter follower. Pin 25 supplies internal audio from a DAC on the chip. See this ...
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4answers
2k views

building an audio amplifier for 2.5 ohm speakers

I recently dug out of my box o' stuff a pair of seemingly decent 2.5ohm bookshelf speakers. I wired them to an old mp3 player I have and while they sound good at low volumes, I get lots of distortion ...