Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers,

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52 views

Troubles with mic preamp for headphones with integrated microphone

I am designing a preamp intended to interface with a microphone in common headphones (e.g. apple earpods, or sony headphones with a microphone) which will then connect to my ADC's inputs. I've ...
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2answers
34 views

Where do these three dc error input voltage comes from?

The book said that there are three unwanted dc error input in an differential Amplifier: Wherein: $$I_{in(bias)} = \frac{I_{b1} +I_{b2}}{2}$$ $$I_{in(off)} =I_{b1} - I_{b2} $$ (V_in(off) is input ...
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26 views

Question about common mode input range

With this drawing I want to simulate the behavior of the following differential amplifier. I only draw half of the differential amplifier. Because I think they are equivalent. But when I simulate it, ...
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4answers
118 views

TIA Photodiode SFH7050

I'm working with SFH7050 chip, it contains 3 LEDs and a photodiode. The datasheet suggests the next circuit: But it doesn't mention how to calculate Rf nor Cf. Which values should I use and how are ...
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2answers
2k views

Will a resistor fixed just in front of an op amp change its gain?

We have a circuit as shown in the image. Now if we didn't have the resistor Rp, the circuit is a simple negative feedback circuit with gain given by -(R2 / R1). But the presence of Rp changes the ...
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1answer
95 views

Is this a good circuit for detecting current path to ground?

I basically need to detect if the switch is closed (the application is a water level sensor where current flows to the grounded tank through the water). Is this a good design, or how can it be ...
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1answer
24 views

Asking about supply voltage of AD8672

Can I Consider this OP Amp "AD8672" as Dual/Single supply Voltage or it is for dual supply voltage only? Also IF it can be used with a single supply voltage, What is its allowable range of ...
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5answers
64 views

How do the collector and emitter terminals of a BJT operate when no power supply is present?

let's consider an example of transistor amplifier: Let's consider the case in which power supply is not connected (so between VCC and GND there is an open circuit). What will I read at the output ...
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50 views

op amp - current source - voltage output

I have the electronic schematic bellow composed with two op amp and I want to determine the voltage output of the X2 op Amp. I m a little bit confusing about the aim of using the zener diode D1 in ...
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0answers
48 views

fast analytical technique identifying poles/zeros using degree of freedom

I encounter some engineers who can quickly spot poles and zeros in the circuit by identifying "degree of freedom". For example, a typical technical discussion goes like : "a miller ...
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0answers
49 views

A kind of current mirror design

Recenlty I saw a kind of current mirror circuit used to provide bias current for a differential amplifier. The circuit is posted below and I don't understand its working mechanism, as well as the ...
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3answers
131 views

How to design low pass filter using Sallen-Key architecture?

I have hard time to design a 4th order low pass filter using Sallen-Key architecture with corner frequency 33kHz and overall DC gain of 0dB. I have f01 (normalized) =1, Q1= 0.541, fo2(normalized)=1 ...
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0answers
48 views

Step response of Power amplifier

i have the parameters for this linear amplifier Swell rate >52 V/µs Bandwidth DC … 5 kHz Power 3 × 30 kVA rise time at nominal voltage (230 Vrms) is 5 µs. and the transfer function is: $$F(s)=e^{-0....
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2answers
45 views

Automatic gain controller gain action

Can you guys explain to me how the turning on of Q2 and the charging of C2 increases the vgs of the FET? An equation would be helpful.
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1answer
24 views

How do you properly offset the input on a DC-coupled instrumentation amplifier?

Given a circuit similar to the above image, where you have a DC-coupled signal that occasionally goes below the in-amp's negative rail (ground in this case because I'm interested in designing for ...
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2answers
52 views

Square wave oscillator on PSpice simulation

I'm new to PSpice and here I was trying to simulate a square wave oscillator using a LM193 on PSpice. Here is the circuit that I've created there: Edit: The capacitor C1 has an IC set to 0 However, ...
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0answers
55 views

Despairing over uA741 as comparator

So, playing around with my first attempt at a circuit using an OpAmp, I am now simply in despair with these 741. Apparently they are "outdated" as any post even related to them is first ...
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2answers
64 views

3 band audio equalizer circuit transfer function

I am trying to find the transfer function of part of a 3 band audio equalizer circuit that amplifies low frequencies but I am confused about the topology. Here is the topology: I was under the ...
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0answers
56 views

Reducing bandwidth of op amp to eliminate op amp parasitic oscillation

I am using few op amps to amplify a signal coming from a FGEN. My signal from FGEN is around 500Khz-7.5Mhz. Now regardless of the supply, even when the FGEN is disconnected and power the op amp using ...
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2answers
47 views

[op amp - Gain current source - current reference]

I have a question about the formula to consider for calculation of the gain for the electronic bellow. Thanks for your support.
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15 views

Difference Amplifier to retrieve sine wave

I have built the following summing amplifier circuit from a Fourier approximation of x(t)= 0.143 + 4/π ∑((sin⁡(2π(2k-1)ft)/(2k-1)). I am now trying to retrieve a sine wave from the output of the ...
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2answers
111 views

How to drive high voltage transistor with low voltage op amp?

I'm trying to drive a darlington pair with 24 V collector voltage with an low voltage op amp. I tried adding a PNP transistor so the op amp just have to drive that single transistor, but haven't had ...
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3answers
122 views

op amps comparator or differential amplifier

I have a part of electronic schematic as described bellow, I'm a little bit confusing about the function of the LM321 amplifier. In this case, can we say that is a differential amplifier or just a ...
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2answers
72 views

Differential amplifier common mode and differential mode gain

I need some assistance on the derivation of the formula for AV(cm) depicted in the figure below. the +/-2 delta_R/R and +/-4 delta_R/R are giving me hard time deriving. The book probably provided ...
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3answers
133 views

How to determine if the feedback is positive or negative in this circuit?

Is the feedback in this circuit positive or negative? How can I know?
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0answers
32 views

2 outputs of same op amp gives different voltages

I am using lm358p op-amp for 2 different heaters I connected both of them in a single op-amp and it didn't work firstly I thought that the problem was thermocouples I swapped them but the problem kept ...
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2answers
47 views

Pre-amp connection problem

I am trying to complete the circuit shown above. I am having trouble as the ground connection is not clear to me. Please help me to complete that circuit. And also tell me how to connect C5 ground ...
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1answer
61 views

Transient Response of AC Coupled Inverting Amplifier

The circuit below is from this App Note. The document describes: The capacitors C1 and C2 need to fully charge for the circuit to function properly. The definition of fully charged can vary depending ...
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1answer
65 views

Anyway to reduce pulse trigger time width without using ne555timer [closed]

Is there any other way to reduce the time width of the trigger pulse wave without using 555timer?
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85 views

Audio amplifier circuit explanation

Recently, I am working with amplifier circuits but circuits available online for an op-amp have some extra components with respect to what we learn in textbooks. I know the basic amplifier components ...
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1answer
53 views

How to design a low pass filter for Fourier Square Wave

I am trying to create a low pass filter with a cut-off frequency of 100Hz to retrieve a sine wave from a Fourier Square Wave. I am only able to achieve a sine wave with transients. How can I edit my ...
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3answers
89 views

Op amp maximum input voltage

Many Precision Rectifier Single Supply Op Amp circuits feed the input AC waveform into the non-inverting (+) terminal of an op amp e.g. see this schematic: Image source: Precision full-wave signal ...
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1answer
91 views

How to explain the peak frequency and resistance relationship in this op amp circuit?

I was studying thid tutorial by Simon Bramble. I changed the original circuit a little bit and this is the subject of our discussion: As you see, R1, R2 and R3 are all 1kOhm. When I run an AC ...
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3answers
96 views

Amplifier power problems, power supply limitations, or end stage base current draw

So I am experimenting with various signal generating, op-amp and power amplifier circuits. And I have limited access to technology. Where I am at, everything you buy is twice the price because of ...
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2answers
72 views

Is it possible to make a ring modulator where we replace the transformers with op-amps?

I've tried making a ring modulator like the one in following picture but without using transformers (as the right ones are quite a bit harder to get and more expensive compared to op amps). I assume ...
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1answer
52 views

Alternatives to op amps LM307N and TL071CN

I'am working on an amplifier/driver circuit for a spring reverb bank. The circuit is from the 90s, but still used: Accutronicsreverb Drive 1 Circuit My issues are the LM307N and the TL071CN. These ...
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0answers
62 views

An all-pass filter with 0 degrees to +180 degrees shift

I need an (for audio bandwidth) all-pass filter that has 0 degrees shift in low frequency and +180 degrees shift at high frequency. The ones here https://sound-au.com/articles/active-filters.htm (...
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0answers
29 views

Changing current output in the attached schematic

I am trying to replicate the results of a paper where a cheap potentiostat is outlined. I need a higher current output than the -200ua to 200ua that is produced by this circuit. Preferably around 10ma....
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2answers
107 views

Chrome plating current control

I am an electronics hobbyist and this is my first attempt at an analog circuit of this type. Mostly I stick to arduino and LED stuff or just wiring up kits, etc. This is my first attempt at designing ...
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0answers
72 views

RMS calculation in cheap microcontroller

I normally see that RMS calculation is done using some kind of DSP or more high end microcontroller. I'm using this microcontroller and I would like to know if it could do RMS. I need to read 60 Hz ...
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3answers
78 views

Operational Amplifier - Virtual ground

In the question above I was asked to solve the general shape of Vout, and the exact values in t=0.5ms,1ms. My question is - can I approximate a constant virtual ground in the negative input of the ...
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1answer
58 views

Using Electro-galvanic_oxygen_sensor ; Oxygen concentration varying b/w 19% to 30% for ambient air (which should be 21%)

We are using Oxygen sensor from SGX Sensortech. The datasheet link is attached here. [link]. We are using ARM Cortex-M7 core. The ADC voltage range is 0-3.3V, it has 12 bit ADC. We are using OPA388 (...
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3answers
86 views

Is there a limit to the number of inputs that can be summed with an op-amp summing circuit?

I'm interested in the limits you encounter if you try to add many inputs into an op amp summing circuit. I've read that the inverting configuration is more natural for adding many inputs since the ...
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1answer
49 views

Effect of high impedance Opamp buffer on current lost

In the below figure, end-user have the choice to output 4-20mA or 0-10V (using MUX control by uC), I have inserted high impedance buffer(The part number is not correct) with the voltage divider to ...
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1answer
44 views

Which switch/amplification method described is better for accurate reading of variable voltage using ADC?

I'm trying to design a relatively accurate variable power supply with 2~24V output voltage controlled from an MCU using off-the-shelf parts. For the MCU to be able to read the whole range of voltage,...
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3answers
108 views

OP Amp as differential amplifier

I'm learning about op amps, and I have the following circuit where the amplifier is used as differential amp Since both inputs are the same, I was expecting the output to be zero. But instead, I got ...
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1answer
95 views

BJT differential amplifier

Is there any reason why the gain of a single ended input BJT differential amplifier, with one Rc, is a good approximation of the value of Adm for a common mode input. The simulation shows the ...
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2answers
91 views

How to design a discrete linear regulator with an opamp and an N-channel MOSFET?

So as far as I understand, the basic idea of a linear regulator is to use a series-pass element along with an opamp with negative feedback to stabilize the output. This is what I usually see as an ...
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2answers
61 views

Low cost op-amp with Common-mode input voltage range of 1.125V

I'm developing a project where an op-amp is configured to bring a input voltage difference ranging from 1.8V to 3V to a output voltage ranging from 3V to 5V. The output of the op-amp will be fed into ...
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0answers
27 views

Differentiator Op-amp with a triangular wave

I’m trying to create a differentiator op-amp. The input signal is a triangular wave of frequency 100Hz and amplitude 1V. The circuit I have designed features a series resistor (Rin) and capacitor. ...