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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38 views

Bootstrapping. Common emitter amplifier

How to properly choose bootstrap capacitor and resistor in the common-emitter amplifier circuit, if we know that the circuit should have a low-frequency 3dB point at 100 Hz? Here is the schematic. : ...
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54 views

Use of Ceramic capacitors in HV system

When I opened the supply board to the detector (Geiger Counter), I got the above circuit. The detector uses a gas-filled tube with a central wire at high voltage to collect the ionization (charge) ...
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Test defect audio amplifier LM386

Following this question I wanted to check if my amplifiers are faulty. I rebuilt the schematic in the datasheet (p.10 9.2.2) and slowly increased Vin. There was no change in output gain when ...
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Questions about grounding schemes when converting a double-insulated audio amplifier into a power supply for a 90vdc treadmill motor

I was given a free Denon AVR3311 AV receiver (a.k.a. audio amplifier) which I immediately gutted and converted to a bench power supply. I combined the "B+" and "B-" rails into a single, ~130Vdc output,...
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Art of Electronics Ex.2.20 Series negative feedback amplifier

Here is the exercise followed by a schematic: Applying the techniques we used earlier, one can show that G(open loop) ≈ 200, loop gain ≈ 20, Zout(open loop) ≈10k, Zout(closed loop) ≈ 500Ω, and ...
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72 views

DC current through diodes in AB amplifier

I can't figure out how the DC current through the diodes is calculated in eq. 8.22 on this PDF from University of North Carolina. $$ I_D = \frac{V_{CC}/2-V_{BE}}{R_f+R_2} $$ \$I_D\$ should be equal ...
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40 views

Can someone how to find this voltage gain neglecting r0

I'm trying to figure out why my professor starts off the way he does when trying to find voltage gain. How he starts off is shown in the last picture. Any explanation would be appreciated.
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55 views

Determining gain, KCL/KWL (Basics)

Below is a pi model schematic of a cascaded amplifier. The goal is to find the gain with Rp as load. So the gain would be: \$ A = \frac{V_{out}}{V_{in}}\$. So i set out to find \$V_{out}\$ in terms ...
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34 views

Noninverting amplifier; Saturation point?

I had to design a noninverting amplifier with a gain of 5. I used resistances; R1= 1k R2=4K. Then it asked as magnitude is increased what value of input voltage will it begin to saturate? Drawing of ...
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23 views

Gain bandwidth product for amplifier

If a question simply asked "What is the gain bandwidth product of this amplifier?" And when I am trying to utilize the equation : GBW = (Av)(BW) I am unsure if I should utilize the voltage gain ...
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56 views

op-amp level shifter

I'm working on a brushed dc motor driver and I have to monitor the current. so I use ACHS-7121 current sensor. This sensor convert +-10A into 0V to +5V and have +2.5V in zero current. Now I want to ...
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166 views

What is this circuit's purpose

The input is a current source (photomultiplier), and the output is connected to a charge amplifier (I belive). I tried to draw the schematics from the circuit board, but I don't know what the three-...
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49 views

Roland Cube 60 (Bass) PWR Amp smoking!

My Roland Cube 60 Bass went up in smoke the other day. (after about 30 years of reliable service.) No blown fuses. Hmm. Opened it up and found that a 1/2W resistor was burned up. Similar issue here: ...
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Designing a bluetooth audio unit for speaker

(Cross posting from Sound design stack exchange since it was declared off topic there) I have a sony speaker from an old Home Theatre System that is broken now leaving the standalone speakers in a ...
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22 views

MOSFET Common-drain amplifier configurations

In my text-book is shown this circuit for Common-Drain Doing practice, I found this exercise What does it change between these two configurations? Voltage gain, input and output resistances, lower ...
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26 views

High voltage pulses amplification

Let's consider this scheme: With this scheme I wanted to get a pulse of duration 10uS with very high amplitude, starting by the same pulse with 10V amplitude. I need to get a peak of about 400V (...
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35 views

Strange MOSFET Common-Source with RD=0

I was trying to solve this circuit(find the Q Point, voltage gain, input and output resistances in midband region, the lower cutoff frequency using SCTC method), but I was confused by the absence of ...
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44 views

Buffer amplifier for DC-1MHz (discrete parts)

I would like to make a buffer amplifier from discrete parts (transistors) which is working from DC to 1MHz. I'm not able to google any schematic or tutorial or app note etc. Everything I found was ...
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Design a passive amplifier

I am trying to increase the amplitude of my generated electrical signal by a passive amplifier. I have seen so many complex RLC circuits. But I have limited space for design, therefore, can I use a ...
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112 views

When doing the DC analysis of a common emitter amplifier, why can we disconnect the parts involving capacitors?

I don't understand why the components involving the bypass capacitors and the coupling capacitors need to "disappear" when we are doing the DC analysis.
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59 views

How much power is needed to run these speakers?

I have couple of loudspeakers. Each is rated for: RMS Power 60 watts Power 75 watts vc Imp 16 Ohms I am going to build an audio amp for those but not sure how much power is needed. I'm concerned ...
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851 views

Does higher impedance speakers generate clearer voice?

I have a PAM8403 based amplifier module and going to build a small portable speaker, mostly to listen to lectures and audio books. The module looks like this: First I attached two 4 ohms 3 watts ...
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31 views

For the network shown in the figure, draw the corresponding Thévenin equivalent circuit and establish its parameters VT and RT

I can't find any examples online similar to this format, please help! Attempt: RT = (2*5)/(2+5) = 10/7 = 1.429 k-ohms VT = 8V + 8V = 16 V Do you ignore the center resistor and just add the voltages ...
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37 views

Amplifier \$I_c\$, \$V_{ce}\$ operating range

In the 10th edition of Electronic Devices from Thomas L. Floyd Example 6-1 provides a way to find the AC model output signal operating range based on the following circuit. I'd like to ask for a ...
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39 views

Reading recommendations to better understand how to understand the intended function of a circuit

This is a general question. Suppose I have a circuit like below from CircuitDigest:  My supervisor said that about the circuit that.. [The] circuit does actually involve an amplifier, even ...
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48 views

How to project a FET transistor as an amplifier?

I am trying to solve a problem on using an FET transistor as an amplifier with the common source configuration. The model should be appropriate for high frequencies. The problem gives the equivalent ...
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45 views

Role of input resistance in LM384 Audio Power Amplifier

let's consider the LM384 Audio Power Amplifier (here the datasheet) Can you explain me why is there the 150k resistance? It lowers the device input impedance, which is not good for a voltage ...
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49 views

BJT Differential amplifier. Tail Resistance. Input Resistance

Here is the schematic of the BJT diff amplifier, I wanted to solve (design). The task is from the book "Art of Electronics". Exercise 2.18. Verify that these expressions are correct. Then design ...
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110 views

Amplifying photodiode current with BJT transistor

I'm trying to develop a kind of light detector. To do that, I'm going to use a photodiode and a bjt transistor to amplify its current. I found a circuit in this tutorial: which explains how the ...
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Music distortion from a Bluetooth board at high volume levels

I have a Drok Bluetooth audio amplifier board that comprised of a TPA3116 audio amplifier, a JL Bluetooth receiver and processing IC and a couple of RLC circuits. I've noticed that when I turn up the ...
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68 views

How do I get the replacement circuit for this amplifier circuit?

The situation is that we are looking at the circuits for low frequencies. This is our general amplifier replacement circuit: And if we look at low frequencies, he presented us with this circuit: I ...
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39 views

Impedance matching an amplifier near 1 dB compression point

I am using a RF amplifier (model: Minicircuits LZY-22+) to drive 6.5 MHz oscillation in a coil. I am using an antenna tuner (model: MFJ-969) to impedance-match the output of the amplifier to the coil. ...
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129 views

Why output signal is not symmetrical? What to do?

I am trying to design a 2-stage amplifiers with first stage C.E with PNP transistor and second C.C with NPN transistor. The amplifier is supposed to have a gain more that 40. After designing the ...
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43 views

Class A amplifier

So i have to make a circuit for my university, and it has to be made in electronics workbench. I tried to make a class A amp after this schematic: And made this in EWB: My problem is that my circuit ...
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55 views

Class AB Amplifier - Q point

In a class AB amplifier, why is the Q point much closer to the cutoff voltage as compared to a Class A amplifier which is at the center. Wouldn't this clip the AC signal if its too close to Vce. ...
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29 views

Find capacitor voltage for dram cell!

I have a mosfet with Vin connected to drain e constant voltage applied on Gate and a capacitor between the source and ground. I believe this is a dram cell. Vo=0 for t<0,Vg=Vstep(constant) and Vth=...
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139 views

Simple Transistor Resistor Amplifier Circuit Question

Can Someone Please Help Me On Solving this. I have tried and stuck..In a point that can I apply Kirchhoff's Voltage Law around R2,R4 loop. simulate this circuit – Schematic created using ...
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52 views

Choosing the proper amplifier

I'm trying to pick the correct amplifier for the following circuit: Rref is 1 ohm, Vref is ground, and RL is anywhere between 0-30 ohm which voult mean that Vout would have to be around 30ohm *250mA ...
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103 views

Input & output resistance in voltage amplifier design

I'm currenly taking a course in Analog Circuits in the university and we got a task that requires us to design an amplifier, with characteristics that depend on our ID numbers. My amp should be a ...
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Is it possible to share a speaker line as ground?

Given the following circuit, how can I use terminal 3 to detect when the button has been pushed? Everything right of the 3 pin terminal is a manufactured device- the Aiphone LE-D. (Also note it's ...
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48 views

Impedance matching in common collector

The last stage of a power amplifier to an 8 ohm speaker is usually a common collector. Now many textbooks mention that it is used as a buffer as it has a low output impedance compared to the speaker (...
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Amplifier Circuit as a Signal Adder

Consider two input signals, v1(t) and v2(t). Each has a source resistance of 10 kΩ. We require the output signal to be the weighted sum of the two inputs, vo(t) = 15v1(t) + 20v2(t), delivered to a ...
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101 views

what is the purpose of capacitors in audio amplifiers?

what is the purpose of capacitors in audio amplifiers? Yea, dumb general question but I dont know like for example in this photo what does that huge capacitor do
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Wondering about the components in a chinese amplifier

I just bought an SMSL Audio SA98E. It is a switched power supply based on the TDA7498E. When I googled images of it I saw that they had different internals. Different components inside. Could this ...
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How can i have the max gain, lowest electric power and max output swing for this circuit?

okay so here's my circuit. R1, R2, VinM1 and VinM2 can be changed in a way to have the max gain, max output swing and lowest electric power used. Also, I need this circuit to be analyzed. In other ...
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60 views

Op-Amp Oscillation

I'm trying to design an inverting amplifier that has a gain of about ~30. It is required to be a two stage design with the first stage being none inverting and have an input impedance of >=500k. The ...
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64 views

Amplifying voltage from an inductor

I have a primary inductor connected to a voltage source with frequencies varying from 100kHz to 15MHz. This primary inductor induces a voltage across a secondary inductor via coupling and I want to ...
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152 views

How to set output resistance of an amplifier to be 50k

I need to build an amplifier using BJTs / resistors / capacitors. It should have specific parameters (up to 5% error), and I’ve reached them all except for the output resistance. The parameters are ...
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63 views

Would a capacitor between base and emitter make relay amplifier less noisy?

I have a single transistor relay amplifier driven by GPIO output of Raspberry PI. The amplifier works reliably and is not causing any immediate problems. Still, if I leave the relay flipping on/off ...
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57 views

Lower than expected power consumption from speaker drivers

I'm using two Visatron FRS 5X-8 Speakers in a project. The amplifier being used is a Dayton KAB-215. Powering the whole thing from my power supply at 12V, I see a current draw of ~50 mA even at full ...

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