An op-amp (operational amplifier) is a high gain analog voltage amplifier with differential high impedance inputs, and a low impedance output. A basic building block in signal processing, like as amplifier or active filter.

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Representing an equation with a simulation of Operation amplifier adder

I am trying to represent an equation (Vf=-3V1+7V2+2) using operation amplifiers. The schematic that I did is: simulate this circuit – Schematic created using CircuitLab but I have ...
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1answer
29 views

Need advices on an AC fan control circuit

I've setup a small system where I can control an AC Fan by a data-acquisition board's DAC. Here is my final schematics(please left-click to enlarge it): The first issue was to hack the manual speed ...
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1answer
22 views

Cut-off frequencies for common mode and differential mode filter?

Attached is the circuit section for the differential signal amplification. The circuit is comprising of common mode and differential mode filter capacitors.So there will be two different cut-off ...
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2answers
52 views

powering op amp current

I think this might be a bit of a stupid question, but I've got a bit of mental block on it. I'm trying to power a CA3140 op-amp. I have a 12V source, and an AMD660 inverter to provide the negative ...
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1answer
61 views

Problem with high-pass filter - signal gets shifted down

I have a problem where I am passing pulses received from a photo-diode into a high pass RC filter. Circuit shown below. The pulses are being received at 25Khz. Before the filter, the pulses are ...
2
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3answers
85 views

Transimpedance Amplifier Photodiode

I have a 660nm LED powered in a separate circuit and am trying to build a photo diode using a transimpedance amplifier but I am extremely confused. I read all the articles on this site about them. ...
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4answers
1k views

What is the use of an op-amp whose output and inverting input are connected to ground?

I am in first year of Engineering school and I was given an assignment containing this circuit, which drives pressure sensors in a pitot tube : I am struggling to understand the whole circuit, and ...
3
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2answers
85 views

OpAmp: Calculating A - MAX(B, 2V)

I require an opamp-based circuit that calculates the expression OUT = A - max(B, 2V), as shown here: There are no strict requirements on the shape or exact position of the transition, however in the ...
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1answer
60 views

Problem with a voltage follower transistor circuit

I'm trying to make a voltage-follower using an LM324 opamp and a BC547B transistor. Below is the schematics I use. Vcc is 12VDC and input is DC varying between 0-10V. I then soldered this on a ...
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23 views

telescopic cascode opamp issue with unity gain buffer configuration

I am reading Razavi textbook Analog IC Design on telescopic cascode. I am confused regarding the calculation result of why it is difficult to implement unity gain buffer. The following is the ...
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2answers
52 views

Trouble with a voltage follower

I'm having trouble when I'm trying to make a voltage-follower from GL324 opamp. I use the following data sheet: http://www.datasheet-pdf.com/PDF/GL324-Datasheet-LGSemicon-558557 And following ...
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1answer
37 views

SMPS buck convrter with PWM controller circuit

Hi there I am designing a buck converter run on PWM circuitry for a uni project to drive a MOSFET switch and keep my output voltage constant. The specs are: input voltage of 20v DC +/- 4 output ...
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1answer
72 views

Using an OP-AMP to obtain absolute value

I want to constantly log the voltage of waveform that is coming off a electromagnetic harvester into a SD card. I wish to use the ADC of an Arduino in conjunction with an SD card to do so. My problem ...
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1answer
37 views

Voltage controlled current source for VLC

Im trying to design a driver circuit for the purposes of modulation of a white LED for visible light communication. The circuit i need to build has to be a voltage controlled current source. The speed ...
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2answers
63 views

Op-Amp Superposition

I know that by the principle of superposition that $$V_{\text{out}-1}=(1+R_1/R_g)V_{1}-(R_1/R_g)V_{2}$$ $$V_{\text{out}-2}=(1+R_1/R_g)V_{2}-(R_1/R_g)V_{1}$$ Could someone please explain the concept ...
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23 views

working of operational amplifiers circuit [duplicate]

IN the Following Circuit, the opamp is neither working as buffer nor amplifier. kindly explain the working of the circuit. Its single supply opamp with 5 volt supply voltage.
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61 views

working of the opamp Circuit [on hold]

In the Following Circuit , how the opamp is working ? its not working as buffer. how the divider from 12 volts has stopped opamp from being a buffer ? thank you
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1answer
33 views

Tips on how to find Vout

Could someone please give me some hints/point me in the right direction as to how to find Vout for the circuit below
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42 views

practical design of integrator circuit with Rogowski coil

I am designing a current sensing device, using a rogowski coil.To give a simple explanation of the Rogowski coil, if I were to disregard parasitic components L2, R1, C1 and R2 the output voltage would ...
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3answers
153 views

why do I get noise on the output of the LM386 when I connect speaker but not when I connect a resistor?

I recently made a circuit to test out LM386 audio amplifier for the first time on solderless board. I relied on the datasheet circuit shown below: First I connected a 7.5ohm resistor at the output ...
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1answer
38 views

Making an LED Transceiver Circuit

I'm building up a project to transmit data from one computer to another computer from a wireless media and I have to use LEDs for this purpose (As per the requirements of the project, so I can't use ...
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0answers
56 views

How does the Wien Bridge Oscillator circuit work

I've built a Wien Bridge Oscillator circuit and used it to generate low-distortion sine waves. But I don't understand how this circuit work. I've read through many resources but yet, I can't ...
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1answer
86 views

This guitar piezo opamp buffer lacks any sort of bass, why?

My preamp in my acoustic guitar died after I put the battery in backwards. I need to replace it, and fast. Piezos have incredibly high output impedance (5+ mohm) so a buffer circuit is used to knock ...
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2answers
50 views

Op-Amp decreasing amplitude of audio signal

For a final project for an electrical engineering course I am taking (my first), we have been tasked with combining input from a small microphone and an aux cord, amplifying it, transmitting it via a ...
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38 views

Open and closed loop gain [closed]

How does the open and closed loop gain affect sinusoidal oscillation. If two circuit have the same amplitude and frequency but one has feedback and the other doesn't, will there be any difference in ...
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2answers
69 views

Isolated 1-10V (or 0-10V) output

I need to control an LED driver with analog 0(1)-10V control input. This control device should be very cheap and compact so until now I made a schematic which uses the fact that those drivers have ...
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2answers
61 views

can i use dual supply op amp in single supply mode?

Can i use dual supply op amp in single supply mode? Is it okay to convert a bipolar voltage to uni polar and then feed it to a single supply op amp(amplifier)?
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537 views

Is this clamping voltage divider for a high-impedance input a good, robust design?

I have an AC input as follows: Can range from ±10V to at least ±500V continuously. Runs from roughly 1 Hz to 1 kHz. Needs > 100 kΩ of impedance on it, otherwise its amplitude changes. May ...
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1answer
23 views

Small signal model for Mosfet…unsure as to whether its common drain, gate or source

I am looking to solve for the input/output resistance in the small signal model for the below circuit. But, I am unsure as to how to set up the model as I can't tell if it is common gate/source/or ...
3
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1answer
75 views

Single voltage replacement for 741 opamp

I am working on a project that recreates the cassette-in port on an Apple II for use in an Apple IIGS. The original circuit used the LM741. The location where I am interfacing my circuit only has +5V ...
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3answers
64 views

Thermocouple Op-Amp - Arduino

First of all, I know that this is not the best way to do this, even more so because I am using the LM358. I don t want extraordinary results. Now, on the matter of the problem. I have attached the ...
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3answers
118 views

Startup transient when using a bipolar opamp as a DAC voltage reference

I have a mixed-signal circuit, with the audio side using a \$\pm15V\$ supply, and the MCU and DACs using a \$3.3V\$ supply. The MCU's internal DAC and two external DACs provide control signals for the ...
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45 views

Thermometer circuit

Can someone help me in understand this circuit? I understand what A1 and A3 are for, but have problem with A2 Op-amp. My guess is that it fixes the diode current to \$i_D = v_{3A2}/R_5\$ but what ...
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84 views

Resistor Load Effect on inverting op-amp

I was reading through some notes a while ago and am struggling conceptually with the ideal op-amp philosophy. This started when I looked at the top figure below, I originally solved it using basic ...
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1answer
18 views

PCM4202 Input buffer

I have a question about the input buffer of the PCM4202 ADC. On page 22 of the PCM4202 datasheet, they describe an input buffer. It's pretty standard with gain and filtering. However, the ADC requires ...
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1answer
51 views

PWM to DC converter with op amp - slowly but steadily rising output voltage

I assembled a circuit to convert a PWM signal generated by an Arduino to a DC voltage in the range 0..10 V. I use the 10k-10u RC filter to convert the PWM signal to DC voltage in the range 0..5 V, ...
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2answers
50 views

Circuit that adds offset if input voltage is negative and subtracts offset if input is positive

I'm trying to build a circuit that will have an input DC signal. I know there is a stead DC offset in the signal, and want to subtract it. I do not know if the input signal is positive or negative. If ...
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1answer
112 views

Measuring Open Loop Gain

I have a question about open loop gain. In the circuit below, I want to measure the open loop gain of the error op-amp. I'm curious if the Current Limiting op-amp will affect my gain. What does it ...
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2answers
62 views

In a non-inverting op-amp, why is it R1/(R1+R2) instead of R2/(R1+R2) in this circuit?

So, why is r1 used in the above formula instead of R2?
2
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1answer
58 views

How to increase an output of opamp in this noise generator?

I'm working on a noise generator for my analog synthesizer and have problems with current design I built. As a noise source I use NPN-transistor in avalanche mode with only base and emitter connected. ...
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1answer
112 views

Are there any circuits to get output as a sum of a set of current sources?

I have 3 current sources (I1, I2 and I3) and I need to get an output of linear summation of the current of these sources. Iout = aI1+bI2+cI3 where a,b and c are gain factors (like 1 to 10 and are ...
2
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3answers
91 views

Operation Amplifier: + and - with equal voltage

I understand the basics of Operational Amplifiers, but I am curious, what would happen if the + and - input pins have the same voltage, does the output pin (x) give a high or a low voltage output? ...
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1answer
52 views

Wien bridge oscillator circuit doesn't work

I've connected the circuit of Fig 3.4.6 in this link which is shown below: Here is the circuit that I've connected: Where in my circuit: R3 = 100 kOhm R4 = 47 kOhm R1 = R2 = 5.1 kOhm C1 = C2 ...
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0answers
38 views

Design a photodiode amplifier [duplicate]

I need to construct the circuit above me. The photodiode has a responsivity of 0.9 A/W, and it is used to detect light at the 1mW level. I need to design a circuit that outputs 3 V/mW. This is what ...
2
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1answer
90 views

How to choose an op-amp used as a buffer [closed]

I am having difficulty choosing an op-amp for essentially a one-off design. All I am trying to do is buffer inputs to a +/- 10V 16 bit ADC. Super high precision is not necessary, but I would like to ...
3
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2answers
116 views

Digital Stethoscope

I am trying to make a digital stethoscope. I have attached a condenser mic on the end of stethoscope. Mic Signal is fed to a pre-amp circuit made through TL072 IC. I've attached the schematic.This is ...
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1answer
55 views

Help comparator circuit for this PWM signal inverter

I have 2 signal (signal on the left) and how to combine those 2 signal into the signal on the right, I have try using lm 741 op amp, but unfortunately the output signal is different from the ...
0
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1answer
45 views

Simulating a Constant Temperature Anemometer

I am trying to simulate the results I see when using a constant temperature anemometer circuit to sense air flow. An excellent discussion can be found: arduino thermal anemometer. Here is my ...
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1answer
60 views

op amp oscillation problem during chip measurement

I had an oscillation problem when testing my fabricated chip. As shown in these figures, the transient waveforms of the op amp outputs got severe oscillations. Ch1 and Ch2 are the two output nodes and ...
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0answers
38 views

ECG Right Leg Drive

this is a ECG circuit.aim of RLD is reducing the effect of noise.the common mode signal taken from both ends of the Rg is given back to the body as a reference. I ...