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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103 views

Need help designing an operational amplifier circuit

I am trying to design an operational amplifier with a gain of more than 200000. My first stage is a differential amplifier with an active load. I am getting a gain of about 1900 from it. Second stage ...
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55 views

Output resistance in negative feedback

I was studying negative feedback in voltage amplifiers. I found this on Wikipedia for calculating input resistance as shown below. Following the similar method, I tried to calculate the output ...
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25 views

What are the qualities that you look for in a 2nd stage LNA?

We are building a multi-stage LNA for a TR module we are building in the 144MHz and 440MHz range. The 1st stage LNA has to be the most sensitive---but what is important to consider when choosing a 2nd ...
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25 views

How would you filter the DC input suitable for use to bias/power an LNA?

We are building a transmit/receive module for the 144MHz and 440MHz bands. As I understand, a good LNA can provide poor performance if the environment or the bias voltage is too noisy. What are the ...
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1answer
66 views

Output resistance of an amplifier

While studying about amplifier, I came across the AC equivalent circuit of the an amplifier. While calculating the output resistance of the amplifier, the input signal was put to zero and the load ...
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2answers
180 views

Can Someone explain how HFE works?

I'm very new to circuits and was confused about HFE affecting collector current in a BJT. How does the base current affect collector current? Shouldn't it just amplifies the current at the emitter and ...
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1answer
34 views

Common Collector Amplifier DC Analysis (why not get the VTH and RTH like in Thevenin's Theorem?)

I looked in the book of Electronic Devices and Circuit Theory and in the section of a common collector amplifier configuration with a voltage divider, it shows that: $$ V_B=\frac{VCCR_2}{R_1+R_2} $$ ...
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18 views

substitute of SE2431l front end ic

I am working on the project with SE2431l front end ic ,unfortunately the lead time of the ic is very much. So i was searching for the substitute. I found RFX2401C but the pin to pin configuration is ...
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2answers
111 views

Remove DC bias without phase shift?

Are there any circuits than can remove DC bias of an input signal without inducing a phase shift? I'm thinking for the input of an amplifier but whatever will work.
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52 views

Difference between a lock in amplifier and an oscilloscope

I'm a physics student and in my lab we are currently dealing with lock-in amplifiers. So far the thing that I found out is that an oscilloscope displays a signal in the time domain and a lock-in ...
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8answers
2k views

Is a transistor truly an amplifier?

My understanding of transistor is that in it a tiny current controls a huge current. I get that concept. If that is the case, it is not amplifying anything in my opinion. Sure it does dictate when ...
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1answer
69 views

What are the resistor values that I should use in order to get 38dB gain? [closed]

I have build a common emitter-common collector multistage BJT amplifier. I want to get an output gain of 38 dB under the conditions of 8 ohms load resistance, 6 volts, 25 mVpp input voltage signal. ...
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37 views

Is it safe to leave the GND from an antenna jack unconnected from an active antenna amplifier?

I need help with trying to use properly this circuit, the original idea came from the late Tony Van Roon who designed it. According to the article it seems that the logic behind it is that the dim ...
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1answer
53 views

Stereo channel strip based on NE5532

I want to build a stereo channel strip, using the NE5532 IC. It should feature 2 mono inputs with volume control, mute switch and pan control going to a stereo output with unity gain. In the schematic ...
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58 views

How can I go about learning to output audio to a speaker using a STM32 board?

I am hoping someone can point me in the right direction. I am trying to learn how to output audio on a STM32 board. The board I have is the STM32F746ZG NUCLEO board. I have small (1-3) second audio ...
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2answers
110 views

I'm trying to build a Common Emitter Amplifier, but nothing is working

My transistor model is BCx19, and I'm trying to get a 10 times gain. I am honestly kind of lost. COuldn't get a lot of info from my teacher, I was just more confused when I asked him.
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49 views

How to sound-amplify my ESP8266

I've set up a ESP8266 to play MP3 radio from a web server, using the ESP8266 Audio library. My circuitry is pretty much like this: My question is, how can I amplify the volume of the sound, as it is ...
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2answers
68 views

Home Stereo vs. Music gear power rating [duplicate]

I see home sound systems rated at 300w, etc. but a 50w guitar amp is massively louder. I assume that the first one is some useless marketing rating, but how are the two figures calculated to be so ...
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3answers
594 views

Irregular common emitter amplifier design

Would anyone know of any merits (or demerits) to the common emitter amplifier represented in Figure 1 in comparison to one of a regular pattern (Figure 2)? Thanks. (The 'DS548' transistor in Figure 1 ...
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0answers
36 views

What's wrong with my experiment to observe harmonics caused by receiver saturation and non-linear behavior?

I've been trying to devise an experiment to produce a third order harmonic in radio receiver that's been saturated, but I'm not seeing the expected results. My understanding of the theory is that when ...
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28 views

Which is the bandwidth of an analog PAM (needed to design an amplifier)?

in a university test, I've been asked to design an amplifier for the following signal: $$s(t)=\left[\sum_{i=1}^{\infty}rect\left(\frac{t-t_i}{T}\right)\right]\cdot Acos\left(2\pi f_0t+\varphi\right)$$ ...
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1answer
51 views

Reverse the drain of a Channel - N Mosfet using a P - Channel Mosfet? [closed]

I am working on a school project which consists of converting audio signal into amplified pwm signal with a tda amplifier (raw) not a complete circuit with resistors and capacitors, then converting ...
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2answers
174 views

Is this IC damaged or fake?

I am trying to test a AD8307. Here are my connections: (pins not shown are left unconnected, and also pin 8). I get a quiescent output voltage at pin 4 of about 850 mV with respect to ground, which, ...
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1answer
43 views

AMC1200BDUBR Gain is 4 instead of 8

I want to measure grid voltage with AMC1200b. I used a resistor voltage divider and I lowered grid voltage from 110v(rms) to 110mv(rms). I fed the 110mv(rms) signal to AMC1200b (for the first side of ...
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2answers
92 views

Same output amplifier

Is there a amplifier that will always put out the same value? The values are ac not dc Example 1: 1 volt signal in=> 5 volt signal out. Example 2: 3 volt signal in=> 5 volt signal out. Example ...
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2answers
30 views

Error: Multiple analyses requested in LTSpice

I am running the following simulation in LT spice but I am getting the following error: Multiple analyses requested .trans 0 100m 90m 1m .op Here is my circuit. ...
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4answers
3k views

Is there a programmable variable resistor

I have a current signal that can vary in amplitude. I currently have a transresistance amplifier which uses 330 Ohm resistors. However the amplitude of this signal can vary and I would like to be able ...
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1answer
65 views

I'm looking for the right audio amplifier, but am lost in a maze as an unexperienced starter

Firstly thanks for helping out! The problem I am facing is that I have to power 24 audio exciters (2W max, 8 Ohm) from a microcontroller which is currently 5V but might be switched to 3.3V later on. ...
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1answer
45 views

Why an does an offset on the reference electrode create an offset on the measure electrode of a pH probe?

I am making an analog front end for a pH probe. I encountered a design where creating an offset on the reference electrode creates an offset on the measure electrode. How does that work? Does the ...
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1answer
63 views

How to prevent single rail ampliier power-on pop sound?

I would like to build a 9V battery powered microphone pre-amplifier and I'm encountering a design problem which I don't know how to solve: I have an opamp that serves as main amplifier which is ...
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1answer
86 views

Bypassing an AC signal in a common emitter amplifier without a bypass capacitor

We all know that we use a capacitor across the lower resistor (Re2) so that the AC will be bypassed through the capacitor and hence no (almost) AC voltage drops across the 2.7k. If that is the case ...
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38 views

Source Follower MOS based amplifier design

VDD = 3V, VSS= ground (0 V), use a current mirror circuit for the biasing. I want to design a source follower with a bias current of 20mA. And also I want to find its power dissipation, 3dB bandwidth, ...
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2answers
62 views

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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1answer
41 views

Stability of a RF Amplifier

In this article a RF Amplifier Design is proposed. It's written that (page 2): In an RF transmission network, if the reflection coefficient of a certain port is greater than 1, positive feedback will ...
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2answers
49 views

Constancy of gain bandwidth product for amplifiers

I've seen the assumption of gain-bandwidth product being constant for some amplifiers. More specifically for a compensated op-amp. Is there any mathematical proof to establish why the product is ...
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3answers
133 views

Low Pass Current to Voltage Amplifier with 2 Op-Amps

let's consider this two Op-Amp amplifier: From what I can understand, it consists of two amplifiers: A current to voltage low pass filter (at left) A non-inverting amplifier (at right) Well, there ...
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3answers
86 views

In a differential pair BJT amplifier, the individual gain of the transistors should be equal. Why am I getting different gain for each transistor? [closed]

Here I have taken a differential BJT pair. Both the individual gains are different and the output differential gain is also different. Is there a problem with my circuit? Why is it happening?
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2answers
62 views

What kind of amplifier do I need for differential to single-ended audio conversion?

This is a follow up to my previous question: For my Amazon Echo related project, I realized that the speakers in the Echo are being driven from a differential amplifier, and not a single ended one. ...
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2answers
76 views

Why does my summing mixer max out at 5.39V when my rails are roughly +/- 11.7V?

I've been working on this project to sum and scale DC voltages from 2 sets of four 0-5V variable voltage dividers, into two separate mixes with identical circuits. In my previous version, I fed the ...
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0answers
29 views

MAX 6675 K-type unstable to say the least

have two breakout boards with MAX6675. I have 3 different K-type thermo elements. The MAX is connected to an AVR (atmega8) for communication, driver my own, communicates to PC on UART. Now none of the ...
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3answers
142 views

Why only common collector method is used in class AB amplifiers?

I have recently started to study about class AB amplifiers online, as a newbie, i have found every schematic of the class AB amplifier is in common collector circuit just like this Schematic i find ...
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0answers
25 views

Connected my audio input to two music systems by splitting the input, but the one with subwoofer produces continuous 100Hz hum

I have 10 year old Creative 2.1 audio system that has fairly capable subwoofer, and combined its input with a TPA3110 2x15W stereo amplifier module (for better treble). When both systems are powered ...
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1answer
47 views

How to properly remove an op-amp from this signal amplifier circuit?

This is a pulse shaping circuit, that has three amplifiers: U1, U2, and U3. The shaping amplifier is the 8pin component far right. Both U1 and U2 serve as "coarse gain," which are activated ...
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2answers
143 views

Resistors in a transistor circuit [duplicate]

I am not an electrical engineer but I was just reading the book - The art of electronics. I am just a bit confused about how to analyze this amplifier circuit. In this case, why are R1 and R2 in ...
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2answers
172 views

How to measure very low current by amplifying it?

I am trying to measure current from a DC circuit. So it basically I am trying to make an ammeter. I am using ACS712 20A current sensor and Arduino UNO. Theoretically, I can measure a minimum of 50 mA ...
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0answers
62 views

Why does it make the composite amplifier circuit stable?

I reversed engineered a headphone amplifier based on composite topology with opa1612 and tpa6120a2. There's two capacitor and one resistor (circled in red) that I don't quite understand. I know this ...
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1answer
144 views

Why does volume above 80% break my speaker (PAM8403, 3w 4ohm, 18650)?

I am new to working with electronics and I am building a simple speaker. The Problem The speaker I built so far (poor sound quality aside) stops working if the volume is above ~80%. By stop working I ...
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1answer
47 views

How to linearly boost the output of a Gaussian shaping amplifier?

I have a pulse detection set up that takes in analog pulses (with relatively long tails, gamma spectroscopy). This pulse is sent into a shaping amplifier, that removes the tail, and shapes the pulse ...
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2answers
33 views

Am I measuring the Op-amp MCP6004 IC output voltage correctly using Arduino

Right now I am testing an MCP6004 Op-amp IC. A sensor in my main circuit going to give me a signal in the range 0-0.5 V max. So, I want to amplify this in the 0-5V range so that my Arduino reads it ...
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1answer
73 views

How can I increase the base-emitter voltage of an NPN transistor in forward active region?

For a project which involves amplification, I think I have to increase the base voltage, keeping the emitter voltage the same so that my circuit will not go out of forward active region as the ...

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