Questions tagged [power-amplifier]
An electronic amplifier that amplifies a low-power signal in order to make it more suitable for an application that requires higher power (e.g. driving a speaker). Power amplifiers have special challenges compared to lower power amplifiers (e.g. a voltage amplifier, which amplifies a signal's voltage but does not provide much output current capability); such challenges include more board space, cooling components that are dissipating high power, etc.
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How can LM386 follow a signal when it becomes negative?
Here is a picture from the datasheet of the LM386.
Obviously, the input signal is swinging above and below the ground, but pin 4 is not connected to a negative supply. It is connected to the ground (...
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Confusion between Class B and Class AB Amplifier
I am reading about output stages of an amplifier and classes of amplifier. The following circuit is named as "Class B" amplifier.
From my understanding, the above circuit should be a class AB ...
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Audio amplifier for school project
For a school project, we have to explain this design of a audio amplifier. We have only been able to understand to parts marked with colored rectangles.
The design comes from the book audio power ...
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What specifically causes damage when a transformer-coupled valve amplifier has no load across the secondary coil?
I'm new to this forum, so be gentle! I'm an electronics and computer systems engineering student, and I always thoroughly enjoy audio circuits, especially examining older valve based designs (I play ...
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Linearity of power amplifiers
How are power amplifiers linear? Although they have some distortion they are still considered linear.
I tried referencing many materials, but I couldn't find an answer. The characteristics of ...
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Why is it preferable to use NPN transistors for both high-current-output devices in a push-pull amplifier?
With reference to the below circuit why is it preferable to use NPN Silicon transistors for both high-current-output devices in a push-pull amplifier?
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Need help with audio amplifier design for loud volume
I'm trying to design an audio amplifier. The preamp stage is a voltage divider CE, while the power stage is a Darlington Class A:
My goal is to amplify a \$48.7\ \mathrm{mV},\ 1.07\ \mathrm{mA}\$ (...
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Audio Amplifier ICs with RC Filters
Hopefully my questions aren't too simple or vague, and will be helpful to anyone else looking for similar information as I am right now.
My electrical engineering knowledge is mostly a hobby/self-...
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BJT base connected to ground and still operates?
When in university I used to get confused how a transistor (NPN) can draw current from ground. I'm now studying power amplifiers and again, this same configuration appears. How does Ir draw current ...
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Are my power calculations on this MOSFET Power Amplifier accurate?
Thanks to the help of electronics.SE, I've designed my first power amplifier, intended for transmitting CW on 7 MHz.
Before I order parts and build it, I'd request a design review.
One important note:...
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How to design wide band amplifiers?
I've been designing microwave power amplifiers and LNAs for school, I design in microstrip and my matching networks usually consist of stub/line sections or similar arrangements, I have also designed ...
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Why is it possible to have undistorted power amplifiers?
In Albert Malvino's book "Electronic Principles," he says there is a 10 percent rule for small signal amplifiers wherein the AC signal current must be less than 10 percent of the emitter current so ...
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In a Class-C power amplifier, what does the resistor in the base do?
Look at the picture, which shows a Class C power amplifier (source). What is the role of the resistance in the base of the transistor, and what happens if it's removed?
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What is the purpose of diodes after RF power amplifier and before LPF?
I am planning to build an RF transmitter using an integrated PA module (RA30H1317M1). While studying schematics of similar transceivers, for example IC-2200H (that also has a PA module) I see all ...
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What went wrong with this class A amplifier design?
I was trying to build a normal class A amplifier, but no matter how hard I try, I cannot find the reason behind my output (blue line) being clipped at the negative cycle of the input (yellow line.)
...
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Why a "Constant Current Amplifier"? [Opamp Labs 440c | SM-100S]
Opamp Labs (which seems to be winding down as of 2024, but is still a company with a venerable reputation) primarily makes/made equipment for commercial Recording and Broadcast applications.
Many of ...
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DC on op-amp input, audio amplifier
I have built the following audio amplifier circuit on a breadboard. The circuit works. However the circuit makes a DC offset on the non-inverting input of the op-amp.
simulate this circuit – ...
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Are there risks to a power amplifier by driving it below its minimum frequency?
I have an RF power amplifier that is rated for operation between 700 and 2700 MHz. What happens if we drive it at a lower frequency, say 600 MHz? Is there an increased risk in damaging the amplifier? ...
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Power Amplifier for Ultrasonic Transducers
I have come across similar questions, but my problem has some specific requirements so I had to ask a new one.
I'm working on an ultrasonic speaker array for my PhD thesis. My work is focused on the ...
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Transistor bias goes negative under input
I am trying to make a simple class A audio amplifier with one transistor (TIP41, NPN) in common emitter configuration as shown in the pictures.
The problem I have is that when I add the input signal (...
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Audio power amplifier features identification
There is the power amplifier circuit here:
How 18k/1k/.0012uF filter works in the input circuit?
It's clear for me that Q1/Q2 is a transconductance stage: voltage in - current out. But where is that "...
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Benefits of a differential PA in an RF power combiner design
Looking at the schematic for the Shure PA770 Antenna Combiner (found in their FCC listing) we can see the design is fairly straightforward, some amplification before combining via a typical Wilkinson ...
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Is this a valid design of an audio power amplifier with bipolar transistors and no capacitors?
I'm concerned about input/output capacitors in power amplifiers and their destructive impact on the sound-wave.
In my understanding, for simple transistor DIY amplifiers you'll need a really big ...
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what is the difference between these two configurations?
I can understand this circuit configuration:
But i don't understand when signal is placed in Qp's base.
In this configuration we don't have VBB/2 in the two base...
Sorry about my english and thanks ...
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Can the DC offset on a line input trigger power amplifier shutdown?
I am looking at a Kenwood HiFi receiver (KR V5090) from the late 90s that sometimes loses sound on one channel.
Granted, it can just be replaced, but I always like to give devices a second chance by ...
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Can 3rd order intercept point be used to extrapolate the power of 3rd harmonic or 3rd order intermodulation distortion at an arbitrary input power?
I'm trying to understand how to interpret 3rd Order Intercept (OIP3) specifications, and whether or not I can use them to extrapolate performances characteristics, other than just as a measure of ...
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DC stability issue with this audio amplifier
This design has a stability issue.
The DC output point (without input signal) should be 0 V with a small offset, but it's not the case, because this point is not stable.
Initially the amplifier had an ...
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Is it a problem to connect a controlled current source in parallel to a voltage source?
Does a similar connection cause conflicts or damage?
An example of situation in which it's used. I've seen it's common practice in RF to put an inductor (RF Choke) between the drain of a MOSFET and ...
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How do you match an LDMOS FET to 50 Ohms?
I'm considering using one of the following LDMOS FETs as an RF amplifier:
AFM907N (8W)
AFT05MS031NR1 (30W)
AFT05MP075NR1 (70W)
The datasheets provide \$Z_{source}\$ and \$Z_{load}\$ metrics for some ...
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RF Transmitter Impedance - Looking from the Transmission Line
If an RF transmitter is designed to transmit into a 50 Ohm load, is the impedance of the transmitter, when looking from the load towards the transmitter, always 50 Ohms?
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Power amp for function generator
I have designed a function generator with the XR2206. That works well.
I can take it up to 2MHz (sacrificing on THD, however).
Where I have failed so far, is the power stage.
I have a supply of +10V/-...
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RF Power Amplifier outputting insufficient power
I'm using an SE5004L 5GHz power amplifier to generate a transmission signal in a radar application. I've designed the output power of this amplifier to be about 26dBm. Unfortunately, the measured ...
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"Pull-up" and "pull-down" or "push" and "pull"?
I thought about this question when I read an interesting comment by @Simon Fitch in his answer.
In the complementary amplifier stage, in total there are three "pulling" elements - Q2 is a &...
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Resistors values for class AB amplifier
I'm designing a class AB amplifier with a vbe multiplier to amplify the output current. I try to choose the resistors values by doing a DC analysis but when I simulate the circuit in AC, the output ...
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Why isn't distortion much of a concern in RF amplifiers?
Class C and class E power amplifiers both distort the waveform yet they are preferred in RF applications. Why?
I mean if the signal is distorted what will happen to the information which was in the ...
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How can I choose the capacitor for a class B power amplifier?
In this class B power amplifier, the capacitor is fully charged when Qmax = C. Vcc and discharges in a negative period. Why is the capacitor full with Vcc instead of another voltage value?
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How does SNR improve with impedance matching in a radio receiver?
I've seen basically every question and answer on here relating to impedance matching, and why you need it in RF but not in audio applications, and I'm still missing something.
I initially was ...
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Emitter follower as single-ended power amplifier
I have seen that the following circuit is mentioned as a single-ended class A power amplifier.
Also, push-pull configuration is mentioned as a better power amplifier, which isn't single-ended, and ...
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What's wrong with my1943/5200 Mosfet Amplifier? Blown on first run
I have just brought an 1943/5200 mosfet based amplifier board. Shopkeeper said it's rated for 24-0-24 AC.
So I connected it with 24-0-24 transformer like this in image below.
As soon as I turned the ...
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Why do I have clipping in this emitter follower
I am trying to design a class A amplifier buffer stage (I know it is not efficient.)
I am starting from the simple emitter follower and the next step is to replace the RE resistor with a current ...
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Drawbacks of Class A push pull audio power amplifier?
I am willing to develop an Audio power Amplifier myself in a Push Pull configuration of two complementary transistors (NPN,PNP).
On the internet, it is found that most of the conventional Class AB ...
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I have read that putting 2 transformers in parallel or in series will increase the output power, how does this work?
I have questions about transformers placed in series and parallel and how they are able to amplify voltage for series and current for parallel without decreasing current/voltage as the case for a step ...
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Audio power amplifier improvement
I need someone to revise/suggest improvement for the audio power amplifier I am designing. This PA is going to be used for driving the horn speaker (8ohm 100W). I decided to start design from scratch ...
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How can I use USB output (5V DC) to power a fan 12V DC load?
I would like to power a 5V DC/0.23A fan (beside another device such as 12V LED lamp, and 12V DC water pump). The only possible power source is using USB output, either from computer, mobile phone's ...
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How does a push pull transistor switch?
I have some difficulties regarding this single supply diode biased push pull amplifier.
Every book and video out there says when one transistor is on the other will be off - just as simple as that. ...
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Why are there three transistor pairs in a class B power amplifier circuit?
I have a class B amplifier circuit to be done in lab. Why are three pair of transistors used in this? I suppose one is a Darlington pair but what is the requirement of the third one? Also, why is ...
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What do the inductors L2 and L3 do in the following rf power amplifier circuit?
I found a circuit online about an rf power amplifier working in the 88 to 108MHz FM spectrum. The circuit diagram is shown below
I understand that an amplifier needs an inductor and a capacitor in a ...
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Effect of (possibly missing) grounds in power amp output circuit
NOTE: It turns out, the ground connections I wonder about below actually are connected (thanks Sim Son in comments), although I still cannot see how they could be connected (additional closeups). The ...
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How to analyze the biasing of the output stage in this amplifier?
My textbook says that biasing current through Q8 and Q9 is about 20mA and through Q10 and Q11 about 100mA. How can I analyze the circuit to get these values with back-of-the-envelope calculations?
So ...
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Resistor network in between SAW Filter and Power Amplifier
I am going through user guide of Microchip's LoRaWan Gateway. The manual is over here. At page 48, I am struck at one resistor network and unable to understand it's ...
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