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Questions tagged [power-amplifier]

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2
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1answer
50 views

Improving Power Amplifier - Digital Bias current set

In the following power amplifier: the MOS bias current is set by VR2. T4 acts as a temperature balance. The ensemble R15, RV2, D5, T4, T5, R14 act as a current source. VR1 act as offset adjustment....
1
vote
1answer
29 views

Calculation of DC power drawn by circuit in Class A power amplifier

simulate this circuit – Schematic created using CircuitLab I'm watching Prof. D.C. Dube's lecture (timestamp included) on power amplifiers, and I'm confused about the calculation of DC power \$...
0
votes
1answer
84 views

Unexpected loadline in ADS simulation

NOTE: This question is related to a homework project. I’m designing a PA for the 850-880MHz band. We have quite a lot of freedom for doing that. Only two requirements are specified: The amplifier ...
0
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0answers
37 views

how to enlarge the reading range between the 13.56MHz NFC reader and tags with ISO15693?

I use TI devices, DLP7970ABP and RF430FRL152H tag. In order to enlarge the reading range, I buy a power amplifier and a large antenna(430mm*330mm). If I only disconnect the original antenna on the ...
0
votes
0answers
27 views

Add IR (infrared) remote control to simple audio amp?

is it possible to add some kind of a remote control receiver to a basic audio amp board that only has a manual volume knob? The IC chip in the amp board is a TDA7498. A general view of the board is in ...
0
votes
1answer
100 views

Isolated High Voltage Amplifier Idea

Test laboratory of our factory asked me to design an isolated high voltage amplifier. Here are the requirements: The circuit will be built with transistors and passive components in the lab. (No IC ...
1
vote
1answer
77 views

How do I choose the power rating of resistors in audio power amplifier?

I read a bit about audio power amplifiers and struggle to understand the power rating of the emitter (i.e. current sharing) resistors in power amplifiers. I refer to this project. [EDIT: schematics ...
1
vote
2answers
80 views

Why should the bias servo transistor not be placed on the main heat sink for a Sziklai pair?

The Wikipedia page on Sziklai pairs contains the following statement (emphasis mine) Sziklai pairs can also have the benefit of superior thermal stability. [...]. [Q]uiescent current is much more ...
1
vote
1answer
45 views

Power amplifier shows 0 input and output resistance

I have a non-functioning transmitter for a radar I've built. When I was checking for shorts using a multimeter, I noticed that the resistance measurements between RFin and GND and RFout and GND of my ...
0
votes
1answer
62 views

alternative amplifier for vibration exciter (shaker)

I am using a second-hand LDS V201 permanent magnet shaker, and would like to use this to test and validate some monitoring equipment. I would like to generate signals suchs as sweep sines, but these ...
0
votes
1answer
33 views

Calculate input resistance of power amplifier

how can I calculate the input resistance of this circuit? Thank you!
0
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0answers
49 views

Amplifying pulse signals causing pulse lengthening problems

I am currently trying to design a circuit that would sense a voltage change at its input, convert that change into rapid "on"/"off" change at output and amplify same switching voltage to high current (...
0
votes
2answers
148 views

Power Amplifier (Darlington) with Power and current limitation

I'm designing a power amplifier and the following circuit is the output stage. My output stage consists of two complementary transistors for both, positive and negative waves but for better ...
0
votes
3answers
129 views

Power amplifier, does this circuit work?

I found that circuit for a power amplifier. Does it work? I want to build one for myself.
1
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0answers
52 views

Built-in power amplifier of the ST7580

The ST7580 is a power line communication device that can be controlled with any host controller. The ST7580 has a buil in power amplifier to allow it to send a modulated signal (0Hz to 250kHz) as far ...
2
votes
2answers
216 views

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 ...
2
votes
2answers
63 views

Question about the power rating of a RF power amplifier

In HMC453ST89's datasheet, it gives the electrical specifications when Vs = +5V: The max. output power is around 32.5dBm, about 1.6W. But for a 50 Ohm load, 1.6W means the peak voltage is about 12V. ...
0
votes
1answer
74 views

How close to P1dB can I go?

I'm trying to decide on a safe input power to a power amplifier. The amplifier in question is SE5004L. The datasheet specifies that the amplifier output 1-dB compression point has a minimum value of ...
-2
votes
2answers
98 views

Stk086 distance between pins? [closed]

I have been trying to make a footprint for this IC, and trying to figure out the distance between pins, it is a 10 pin ic what do you think the distance will be? What is the normal distance between ...
1
vote
1answer
388 views

IR2110 driver output causing shoothrough despite deadtime

I'm having trouble with the ir2110 output. I'm working on a class d full bridge amplifier and I use 2 ir2110 to drive 4 irf540N mosfets. The switching frequency I use to generate the PWM is 240kHz and ...
0
votes
2answers
108 views

How to design and build RF amplifier, that work in 450Khz [closed]

I have a schematic, that is a sine generator and mixer that does AM modulation. How to design and build an RF power amplifier and build a compact antenna. The goal is to transmit signal up to 50 ...
0
votes
2answers
73 views

Maximum output power of a PA

I was discussing with a friend about maximum output power of a (class A/B power) amplifier (for example if the device following the PA can only tolerate a certain amount of power). If the input power ...
1
vote
2answers
586 views

Biasing Class AB power amplifier with MOSFETs

I am having trouble getting the resistor biasing to meet a minimum 1.25W at the output: Note, the distortion and watt meter. I was told the SPICE parameters for the FETs didn't really matter. (...
0
votes
2answers
61 views

Understanding of class-AB currents

I am trying to understand a simple class-AB output stage. The bias voltage for the transistors is made by using two diodes. The following picture show the circuits. The currents drawn are how, i ...
1
vote
2answers
235 views

Design a tank circuit for class C power amplifier using ADS

I am trying to figure out the best values for the tank circuit values (L and C) in order to compare the amplifier's efficiency with the output power I have chosen the tank value L1 and C7 to resonate ...
0
votes
1answer
32 views

Vibe Table: Increase Peak Force Output?

I'm driving a small, benchtop vibe table (shaker) with two Crown DSI-1000 PA's, and also cleaning my signal with a DBX 231s EQ. Currently running the system at 6.8 GRMS, but I'm looking to increase my ...
2
votes
0answers
357 views

TDA7294 100W Audio Amplifier Causing Unexpected Problems

This is the circuit I will be referring in this question: TDA7294 is described in this data sheet. Upper IC with added external components is a well-known circuit and can be found on many websites ...
1
vote
1answer
97 views

RF power amplifiers and preventing damage when the antenna is disconnected

I'm looking at Wi-Fi 2.4 GHz power amplifiers and I can't find a single high power (500 mW) one including a system protecting it from damage. I can, for example, find some ~ GHz PA with protection ...
0
votes
1answer
43 views

AWR PA Output Power Simulation - Credible?

I'm working with the SKY65111-348LF power amplifier from Skyworks and wanted to obtain some idea of its performance using AWR Microwave Office. I'm not sure if my process is correct and wanted to have ...
1
vote
0answers
418 views

Increase output power of simple class AB audio amplifier

How could one increase the output power from a class AB amplifier circuit like this one? I wish to increase the output power to around 2W. The above picture is simulated with a 200mV amplitude, 5kHz ...
0
votes
2answers
60 views

Conventional current in a power amplifier?

I recently learned that electricity doesn't actually flow from + to - but the other way around.. So my question would be: if I was using a 2 channel power amp and connected a speaker to it with the ...
2
votes
2answers
157 views

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 ...
2
votes
2answers
117 views

Can someone help me with this power amplifier problem?

Wire the circuit shown:

 R1 = 68KΩ R2 = 10KΩ R3 = 10KΩ R4 = 200Ω ( two 100Ω in series ) R5 = 2.2kΩ C1 = 0.1 µF C2 = 0.1 µF Q1 = 2N3904 
 Set the sig. Gen to 50mv RMS.  With frequency ...
0
votes
3answers
282 views

15-20W amplifier circuit

I'm trying to build a small radio amplifier which will deliver around 15V at 1A at 250kHz from a 0.2V input of the same frequency. I have searched for and tried as many online circuits as I can which ...
6
votes
4answers
1k views

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 ...
1
vote
1answer
578 views

Calculate the total max power dissipation in CLASS AB push pull for reactive loads

As worst case we can assume in reactive load the same power dissipation with the resistive part of that load. Thus for a 8 ohm impedance with phase angle of 60°, we can use \$R_L=0.5*R_{Reactive}=4\...
0
votes
1answer
52 views

Using an RF adapter to improve LTE signal in the house

In my apartment, the GSM signal is very scarce, if not absent at all, except for a few spots, where there's a decent LTE signal and I can browse internet reliably. In order to improve the reception ...
1
vote
2answers
347 views

Class A power amplifier: power dissipation

Let's consider the following class A power amplifier: And here is the time-domain simulation of the power dissipated across the transistor: As we can see, the power varies from approx \$0.1W\$ to \$...
4
votes
2answers
1k views

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 ...
1
vote
1answer
269 views

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 ...
0
votes
2answers
274 views

Push-pull amp in class A what it mean

I take next sample schematic. This is only an output stage of any real power amplifier. It's clear when it's work in B-class the every BJT amplify only one half of input signal. But what it means if ...
1
vote
1answer
162 views

Two diodes in input stage of power amplifier

Some of the power amplifier schematics include diodes in input stage like below. What is the purpose of them?
0
votes
0answers
42 views

Difference between two equal valve tubes

Is there any difference in "Plate Voltage"/"Plate Current" curve between two real vacuum tubes 12ax7?
0
votes
1answer
376 views

Impedance of an Electret Mic

I have an electret mic for the design of an audio amplifier using input and output stages. How can I measure the impedance of that mic?
0
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3answers
98 views

class AB amplfier help

as a class project, we were given a circuit schematics of a low distortion audio power amplifier. and we were asked to simulate it, i did that no problem. however I am trying to understand the circuit ...
0
votes
1answer
368 views

How RF Choke doubles Vcc at collector in BJT Power Amplifier

I'm trying to analyze a class A RF power amplifier as represented in the picture. The main thing I'm trying to understand is how the collector voltage can go to 2x Vcc as according to this page. ...
-1
votes
1answer
56 views

Power Amplifier inside an OPAMP

Here is a simplified schematic diagram of one of the operational amplifiers inside a TL08x. The Diagram I wonder why a power amplifier is used ? (on the right side) What is it good for ? Thanks in ...
3
votes
3answers
539 views

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 "...
0
votes
3answers
158 views

Differential stage Av value with current sources

Why all books told that Av differential of an differential input stage in power amp is very big? Ad = Rc/re, but if there are current sources in the emitter and collector circuit they will have too ...
-3
votes
2answers
118 views

Power amp Av with current source

How could I calculate the voltage gain Av for the following power amplifier diagram? Here there is an example how to find it but the schematic doesn't use current sources and use the voltage drop on ...