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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)

7
votes
1answer
2k views

Charging two lead-acid batteries connected in series, separately (with two solar panels)

I have two lead-acid batteries connected in series to produce 24V. They are powering an audio amplifier. I'd like to be able to charge them while they are powering the amplifier, with solar panels. ...
13
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4answers
5k views

Alternatives to transistors

I'm trying to think of alternatives to transistors, simply because I'm curious. I don't care so much about the amplifying characteristics of transistors as their ability to make logic gates. Here's ...
4
votes
3answers
8k views

How are RF signals amplified?

So this may be a terribly stupid question but since my RF knowledge is fairly limited I'm asking it anyway. Let's say you have an AM signal that's 5Vp-p at some frequency. To amplify this can you ...
8
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4answers
3k views

Controlling a current with another - home-made alternatives to the transistor?

I have a very basic understanding of how a BJT or a FET works, but I think I got the idea. They are awesome in all regards, except one: you can't make one at home without hot ovens and scary chemicals....
0
votes
1answer
1k views

Decrease Impedance at Higher Frequencies

I am trying to see if I understand how impedance works correctly before I build this into a real circuit. Basically I have an inductor (helmholtz coil) driven by a function generator, now by itself we ...
1
vote
1answer
647 views

What potentiometer should I use for this phono pre-amp?

Please consider this DIY phono pre-amp. The text states, that resistors R9 and R22 may be exchanged for potentiometers for gain control. Since the circuit uses 1.2kΩ resistors for R9 and R22, I was ...
0
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1answer
1k views

How to Increase RF Amplifier Efficiency?

I've inherited another engineer's RF design and I would like to increase the transmitter efficiency. It's a 406 MHz radio that is using 14W to send out 5W (36%). The amplifier in use is http://www....
0
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2answers
2k views

Power Calculation of an Amplifier

Here is a simple audio amp. Is there an easy way to calculate the power it gives? edit Resistor value, input level and speaker impedance changed.
4
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4answers
5k views

Common Emitter Audio Amplifier

I'm tring to build an audio amplifier. I decided to use a basic common emitter amplifier circuit as a starting point. Here it is: I have some questions about the circuit. 1-) What transistor can I ...
-3
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3answers
2k views

Calculating the power of a simple amplifier

I found this circuit on internet. It says it's a 1w amplifier. There is no explanation about how that is calculated. How could the power of this circuit calcuted? (input is a radio) And is there any ...
1
vote
2answers
125 views

Amplifier theoretical analysis problem

I have this problem in a book and I've did good through the entire problem until I had to calculate current gain. I've been stuck for the past 30 minutes. The formula I get is different from the one ...
0
votes
1answer
722 views

Voltage source for single transistor audio amplifier

Here is a simple audio amplifier with an npn transistor. What should be the value of voltage source V2? How can I calculte it?
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0answers
143 views

Basic audio amplifer circuit with transistors [duplicate]

Possible Duplicate: Simple Audio amplifier Using Transistors I'm looking for a basic audio amplifier(1w - 0.5w) circuit which is designed with transistors. Could you help about that?
1
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5answers
5k views

Problems in 8W Audio Amplifier using TDA2002

I have made an amplifier using TDA2002 but it's not working properly. Pot. R1 is not included in mine as it doesn't make a lot of difference and produces noise when I try to adjust the volume. How ...
4
votes
2answers
3k views

Digital Switching for Audio

I want to be able to digitally switch the input of a line-level preamplifier. I was considering using relays to physically connect or disconnect each source to the input of the amp, which would be ...
0
votes
2answers
3k views

Is feedback transfer function the same as the transfer function for the whole circuit?

I have a circuit very similar to the inverting band pass filter circuit here: I was asked a question about the circuit's feedback transfer function. Is this the same as the transfer function for the ...
2
votes
2answers
989 views

How does this circuit attenuate high frequencies?

I understand that this circuit could be used as a treble control circuit with high frequency gain occuring when R3 is set so a=b (we'll call this k=0), and high frequency attenuation occuring when R3 ...
2
votes
2answers
1k views

Why can't a feedback network use a capacitor? [duplicate]

Possible Duplicate: Basic Frequency Control Circuit In the following schematic, why can't R4 be taken away and the feedback network pass output feedback through C2 and R2?
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1answer
263 views

Types of amplifier - what is the difference?

What is the difference between an open loop amplifier and a voltage follower (unity gain buffer)?
17
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6answers
56k views

Why is feedback required in op-amp circuits?

I understand that, in order for an op-amp to function correctly, a DC feedback loop from the output to either the inverting or the non-inverting input (depending on the external circuitry) is required....
3
votes
4answers
3k views

Basic Frequency Control Circuit

How does R4 prevent the output voltage drifting towards one of the supply rails to the op amp? I understand that R4 has to have a high resistance but I do not know why? Here is the schematic which is ...
0
votes
2answers
1k views

Amplifying strain gauges on an arduino

I have 4 standard mild steel foil strain gauges bonded to a steel bar in a wheatstone bridge arrangement. They are implemented into a circuit with the INA 125P amplifier. I only manage to use about a ...
12
votes
4answers
66k views

What is the definition and purpose of a pre-amplifier?

I find in many places mentions of pre-amplifiers being used to boost audio signals prior to feeding to a power amplifier. Wikipedia's article on pre-amps gives some hints at their usage, but it doesn'...
0
votes
3answers
803 views

Switch at output of operational amplifier

I'm currently designing an active filter which has to pass an analog signal between two cables (PLC). I'd however like to not let it pass in case the signal is already present (up to a certain ...
4
votes
2answers
3k views

How do I use a clipping Zener at the input of an Opamp inverting amplifier?

I have a \$ V_{in} \$ signal for which I cannot guaranty that it would have an upper limit. I want to clip this input signal to a limit (e.g.; 8.2V) with a circuit like above. Is this circuit alright?...
1
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1answer
4k views

How to amplify an electret microphone

I need to amplify an electret microphone for use with an Arduino Uno. I have a few capacitors and resistors and several transistors one of which is an N-channel. Any ideas? Can you please also provide ...
0
votes
3answers
260 views

Lower Voltage RF Amplifier for 400 MHz

I'm using this Mitsubishi RF amplifer in a portable device. The Mitsubishi amp operates well between 7V - 9V. But I have to interface with a power source that gives 1.5V, and stepping 1.5V up to 7V ...
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votes
1answer
241 views

Amplifying PWM to solenoid

I am driving a solenoid with a DRV103 (a driver for inductive loads by TI), but I need to allow more current to flow to the solenoid than the DRV103 can output. Initially, I tried a simple common ...
1
vote
2answers
993 views

Good LCD for clean mounting in hobby project?

I'm refurbishing an old Kenwood amplifier--- removing the old faceplate and adding a board with a microcontroller, multiplexer IC, digital pot for volume control, IR receiver, etc. I'm also ...
21
votes
2answers
18k views

BJT in Reverse Active Mode of Operation

What will happen if for a BJT transistor it's Emitter terminal is treated as collector and collector as Emitter in a common Emitter amplifier circuit?
5
votes
2answers
2k views

LM386 amp circuit lag

I'm building a motorcycle intercom and am using the LM368 IC for my amp. My circuit works well (surprisingly, I'm new to this). I've got a button which I use as a push to talk switch. This works for ...
1
vote
2answers
2k views

detecting low signal levels with a transistor

This question made me wonder. Say I want to drive a LED when a small level audio signal is present. I understand how to do this with an opamp, but how about a transistor. You'd have to bias it so that ...
1
vote
2answers
2k views

Simple and powerful audio amplifier around BA4558?

I have two BA4558 ICs from an old home stereo. I tested them with simple negative feedback circuit for each channel and with power supply of +/- 6V. The speakers I used are most likely with 8 ohm ...
0
votes
3answers
482 views

The need for a Comparator

Hello i have an op amp shown here: If i connect a speaker to the output of it the audio signal is amplified. So far so good. But if i connect an LED to the output of the amplifier it doesn't turn on....
4
votes
1answer
9k views

In Common Emitter Amplifier Circuit ,Emitter Capacitor effect

I was wondering about the Effect of Emitter Capacitor in Common Emitter Amplifier? It is Suggested that Putting the Bypass Capacitor the output voltage gain is increased but how? As we want more ...
1
vote
1answer
597 views

Impedance for Helmholtz Coil Connected to Audio Amplifier

I am trying to design a Helmholtz coil, that will have an impedance of about 2 ohms (the reason for this being that I am going to hook it up to a audio power amplifier, so to get the same wattage ...
6
votes
3answers
2k views

Can someone explain this tube amplifier circuit for me?

I have a tube radio that has really low output (I mean the sound is barely audible at full volume). Probably some capacitor in the LF amp failed. However, after I downloaded the schematic diagram, I ...
7
votes
2answers
2k views

Why would a Diff Amp require both inputs to have a DC path to GND to work?

I'm looking at using a NI PXI-6255 DAQ card and I noticed in the manual it says "Both inputs of the (diff amp) require a DC path to ground in order for the (diff amp) to work." Is this a common ...
2
votes
1answer
5k views

Combine left and right channel at speaker level

I recently started a project to build an inexpensive speaker/amplifier that is portable enough to take outside easily. I purchased a center-channel speaker from a thrift store for $6 and an amplifier ...
5
votes
4answers
17k views

Why doesn't my transistor audio amplifier work?

I'm a newbie to transistors. Could anyone explain why my set up doesn't work ? The transistor is a 2N2222 NPN BJT, and the microphone is just a standard earbud. The loudspeaker is just one I ripped ...
1
vote
2answers
1k views

Short circuit protection in simple audio current amplifier

In my class, we are to design a current amplifier with short circuit protection. In our design, we utilized 2 emitter follower amplifiers (Q3, and Q1). We then added Q4 and Q7 to lighten the current ...
2
votes
3answers
8k views

DIY simple line out converter for “floating ground” car head unit?

On a 25W max power (10V p2p @ 4ohms) balanced (push-pull) high level output factory car audio head unit from which I need to feed a mono amplifier (for subwoofer) that only has an unbalanced line ...
0
votes
1answer
381 views

How do I get 15V from a 34V power supply?

I have an audio amplifier with a regulated power supply putting out around 34V DC. I would like to add a preamp which requires on 15V. How would I draw 15V from the main power supply?
5
votes
2answers
2k views

100W Low Pass Filter

Currently I have a 60W amplifier for the 400-500MHZ band with a 50Ω impedance. In order to prevent jamming other frequencies I will need a low pass filter to block any frequencies above 500MHZ. I just ...
3
votes
2answers
207 views

Is there an amplifier such that the gain is equal to the ratio of two potential differences?

I have been toying with some alternatives to transistors in building logic gates. I am particularly interested in the device I tried to summarize in the title of this post. The chip would have 8 pins: ...
1
vote
2answers
677 views

Flipping a signal

I've an input of two input lines, one being connected to ground and one carrying the signal (measured to ground). The output should be three lines with one being ground and the others measured in ...
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votes
1answer
4k views

How does transistor amplify current? [duplicate]

Possible Duplicate: I don't care how a transistor works, how do I get one to work? Basic questions about transistor amplification I have heard transistors are used in many electronic ...
16
votes
5answers
59k views

Simple Audio amplifier Using Transistors

I would like to build a simple audio amplifier using transistors. I know there are IC designs specifically for the task. But i want to use transistors so i can learn how to use them for amplification. ...
1
vote
2answers
1k views

1.8v GPIO controlling 5v 10mA solid state relay

I have a Crouzet 84 134 900 solid state relay that I need to control with a 1,8V GPIO output from a Gumstix Overo Summit expansion board. I've tried the circuit drawn up for me in this answer, however ...
0
votes
2answers
251 views

Is it possible to mod a class 2 bluetooth device to work as a class 1 device?

I have two Microcontrollers which communicate over a bluetooth link (serial link, like RN-42). So far so good. Unfortunately the device is listed as a class 2 device and I noticed that the distance is ...