Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers,

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2answers
21 views

How to apply high gain to filtered signal without shifting voltage level?

I have an op amp gain circuit at the output of a 2 stage filter. It seems like at high gain settings (x500), the steady state voltage shifts significantly. I am trying to keep it at ~1.7V and it ...
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2answers
21 views

4-20mA to adjustable set point relay

[![Why doesn't this work? I can adjust pot and relay will energize. 4-20mA will not energize relay. ]2
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36 views

How do I design this op-amp circuit? [closed]

Using the parameters given in the picture, how I design this operational amplifier? I just can't approach this problem.
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40 views

How to understand signal inversion and current flow through OTA?

In the following example schematic for an OTA, transistor M4 is said to be non-inverting input while M3 is the inverting input. The given explanations are short and i find them rather unclear. M4 is ...
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2answers
60 views

How do I connect a 0-10V analog input to MCU with high input impedance?

I'm trying to connect a 0-10V analog input value to my MCU which is running on 3.3V. I used the below circuit but when the input is floating I read about 0.3V on the analog input. I need to eliminate ...
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2answers
45 views

Values of currents in inverting and non-inverting terminal of Op-Amp

In the given solved example from a textbook on electronic devices, the author has use the voltage divider rule after assuming \$V_{s2}=0\$. Clearly for equation 1 to be true, the current in the non ...
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2answers
46 views

voltage to current converter using op-amp and MOS

I came across voltage to current (V2I) converter circuit. and I found Iout=Vin/R1. I have a few questions about it: I believe the op-amp is in the negative configuration because v(3) & v(2) both ...
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3answers
77 views

Why isn't the input impedance mentioned in the datasheet of the AD8597 operational amplifier?

I am trying to look for a high input impedance op-amp to use as a buffer to prevent source loading. When I started checking the input impedance value for different op-amps, I noticed that some of the ...
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3answers
75 views

Current mirror with mosfets

This is a current mirror circuit with 2 op amp stages. First stage on the left Voltage from a DAC gets fed into U1 which creates a reference current through Rmir (via the N channel MOSFET) by sensing ...
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1answer
31 views

Matching line driver output impedance over wideband

I'm designing a high impedance line tap for 10-10GBASE-T ethernet signaling. In the AFE I have a JFET LNA for high input Z which goes to a var. gain amplifier that is a fully differential ADC driver. ...
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1answer
43 views

What is the expression for the load current of the following Operational Amplifier circuit?

I have been battling to find the theoretical calculations to find the expression for the load current of the following Operational Amplifier circuit exercise I have in my "Electrical Engineering, ...
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31 views

What is Zin when EN=1?

The opamp functions only when EN=1, otherwise it is off. When EN =0, Zout = 6kohm. Also, what does the opamp being "off" imply? If the opamp is off, does it mean that no current flows ...
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51 views

Help with designing a suitable 12-to-5 V voltage converter using an op-amp and a diode

The question ive been given: My work up to now: However, I do not know how to calculate the values of R1 and R2 (assuming I am correct up to now). can someone point me in the right direction such as ...
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58 views

One milliamp current source for RTD

I am trying to design a one milliamp current source (Howland current source) with a precision of +/- 1 uAmp. The current source will be used to measure temperature with a 3 wires RTD sensor (H-T-01-12-...
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44 views

2 phase ac servo motor operation in cotrolling load position and direction [closed]

Hello can someone explain to me how a 2-phase AC servo motor can control the position/direction of a load
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4answers
77 views

Subtractor op-amp configuration to find the diference of 2 signals

How can a differential op-amp be configured in a way that it doesn't amplify but only takes the difference between the signals at the inverting and non inverting input?
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1answer
122 views

Powering opamp from unregulated DC-DC Converter?

When using one of those unregulated, isolated DC-DC bricks (its output voltage can be as much as a few volts higher than its rating and varies with load) to power an opamp is a voltage regulator a ...
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0answers
38 views

Unwanted negative spike on the output of resetable charge amplifier

I try to simulate charge amplifier, it will be used as a first stage for photomultiplier tube. It doesn't have resistor in parallel to feedback capacitor (C1), instead, when output voltage is close to ...
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3answers
54 views

Photocell comparator circuit using LM339

How to prove this mathematically?
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0answers
11 views

Oscilloscope not visible in PROTEUS simulation

I tried simulating astable multivibrator using OPAMP. At one instant i got the oscilloscope but wasn't able view the waveform. I tried running again but this time there was no oscilloscope visible. ...
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1answer
86 views

Concept of Bootstrapping in Electronics

I was trying to study about bootstrapping in electronic circuits. When I checked in Internet Wiki says it is a method to improve the input impedance of an amplifier. In the power electronics context, ...
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1answer
45 views

Amplification of Sensor

How would one can amplify a sensor with an internal resistance of 80kohm (produces a Voltage of 500uV). Which opamp can I use? Which type of opamp configuration can give me accurate results? Accurate ...
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1answer
25 views

What voltage or node are the BJT substrates connected to in a bipolar process opamp IC?

I've been recently experimenting with converting transistor-level SPICE models of ICs into subcircuits. One thing I try to keep consistent with my subcircuits is that they remain floating; i.e. no ...
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3answers
53 views

LM318 Voltage Follower Self-oscillation and Output Noise

I've been trying to tame an LM318 opamp in order to replace the LM741 in a circuit because I need to buffer a higher frequency sine wave than the LM741 likes (1Mhz). The datasheet shows the following ...
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1answer
61 views

Working of op-amp based current source

Can anyone please explain me the working of the circuit attached? I believe the op-amp U1 is connected to provide a stable DC voltage at the non inverting terminal of U3. Is my approach correct? The ...
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1answer
388 views

Op-Amp output inconsistent with theory

I was just playing around with a few Op-Amp circuits, and suddenly got stuck on this simple one. As the circuit shows, the Op-Amp output is connected to its non-inverting input terminal, so it should ...
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2answers
33 views

Error in the minimum value of the operational amplifier output

I designed a circuit to control the speed of a 24V coller. For this I used the operational amplifier TCA0372DW. As I am going to control the output voltage through ...
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3answers
146 views

How to electronically generate exponentially growing sinusoidal signal

How can we generate exponentially growing sinusoidal signal (further describes below equation and ) using a simple analogue circuit (e.g. op-amps, transistors, or oscillator)? Mathematically, \$v(t)=...
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2answers
68 views

How does a comparator based crystal oscillator work?

I'm a newbie here. Now I want to design an oscillator circuit to drive QCM-Sensor. Then I have found a circuit from the datasheet of comparator LT1671. It looks just like a relaxation oscillator with ...
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2answers
101 views

Can you use an op-amp like this to detect current?

For a model train track, I'd like a simple circuit which can detect current. In the past, I used an opto-coupler in combination with 2 diodes. A current flowing through these diodes would cause a ...
2
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1answer
51 views

Finding the transfer function of a opamp circuit with 3 opamps

I have the following circuit: I know that \$\text{sig}_+\$ is a voltage that is \$n\$ times bigger than the voltage at \$\text{sig}_-\$. Question: If \$R_g\$ is a coil with the value \$63\space\text{...
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1answer
40 views

Op inverting amplefier circuit

i am using the LM741 amplefier i want to invert a negative voltage (-10V) to positive voltage (1V), my problem is : i dont get the 1v DC at the output. i get an ac signal at my oscilliscope. and i ...
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2answers
101 views

Gaussian signal generation circuit

I was studying op amp application and saw the square wave, triangular wave, sine wave. I was wondering if it is possible to generate Gaussian shape wave with op amp. I am basically trying to modulate ...
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1answer
54 views

Find the differences between two signals with an opamp

I have been trying to find an answer to this question and I am sure I probably just don't know what the circuit is called so I am unable to find it. Basically I want to take two input signals that for ...
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1answer
46 views

Increasing the input impedance of analog input using an op-amp buffer

I'm trying to sample a 0-10V DC voltage as an input to my circuit. I use the following circuit to achieve this: simulate this circuit – Schematic created using CircuitLab The problem I have is ...
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0answers
35 views

How to analyze this bandstop filter?

This is a Sallen-Key second order notch filter(bandstop filter) : This filter attenuates the frequency at \$f_0=\frac{1}{2\pi RC}\$. But I don't get how. How should I analyze this kind of circuit? ...
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2answers
76 views

Op-Amp Comparator Testing

I am having this op-amp Comparator. My circuit is similar to this circuit present in the datasheet of the IC, page 21. I have this circuit now in my board which I want to test. I have never tested an ...
2
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1answer
114 views

What is the difference of cutoff frequency to -3dB frequency in an active filter?

This table shows the K values of a particular Q value on a Sallen-Key active filter: Why is the \$K_c\$ value (cutoff value) different from \$K_3\$ value (-3dB value) on all Q's (except 0.707 which ...
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2answers
51 views

Is there a reason the offset of this opamp is done like this?

I recently found this schematic from a project at university (drawn by our lecturer). It's a low pass filter that also adjusts the gain, and adds an offset of 1.5 V (the input signal can be positive ...
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1answer
43 views

Op-amp circuit oscillation

The ideal op-amp is connected to a power source \$V_s\$ at t = 0. Initial charge on the capacitor is 0. Then it is given that \$V_{OUT}\$ swings to positive value and \$V^-\$ starts increasing. \$V^-\...
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66 views

Unexpected noise at low pass filtered output

I am trying to capture and filter a PPG signal using a simple phototransistor and an IR led. I have hooked the emitter to a Bessel low pass filter so as to get rid of high frequency signals. Below is ...
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3answers
66 views

op amp biasing… why are voltage sources reversed biased +/-?

I'm still trying to understand the theory of audio signal processing, namely guitar amplifiers. The main thing that got me started down this path was a broken amp that I have. I have since figured ...
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1answer
35 views

Op amps with load impedance matching

I have a THS3491 Op amp, and want to use non-inverting configuration. Reading through the datasheet, all the specs are defined with \$R_L=100\Omega\$. So, does this mean I have to attache \$ 49.9\...
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2answers
63 views

Does anyone use Statistical Element Selection for matching integrated circuit components or is this a university exercise?

I have to fix the transistor mismatch on a finfet amplifier design. I've seen lots of papers on Statistical Element Matching, all from universities, but haven't seen anything reported by companies ...
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4answers
90 views

Can a piezo disc be connected directly to a op amp?

I'm trying to use a piezo disc as a sensor do detect slight vibrations, I see the signal on an oscilloscope, it needs to be amplified. But I can't manage to amplife it. For this, I wanted to use a ...
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2answers
176 views

Input impedance of op-amp circuit

All opamps are ideal. The question is to find the input impedance Zin(s). Using KCL: $$I = (V_i-V_{o2})/R_1 $$ $$V_i/R_4 = I-[(V_i-V_{o2})/R1 + (V_i-V_{o2})/R_2] -[(V_i-V_{o1})/R_3+(V_i-V_{o1})sC]$$ ...
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2answers
84 views

Unexpected results in voltage to current converter (simulation is Ok)

The circuit below shows a Voltage to Current converter based on a DAC, opamp, transistor and switches. The last one, allow to have a bipolar signal output. During the experimentation, the DAC is ...
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0answers
33 views

Is there a buffered/high impedance voltage monitoring circuit with voltage limiting?

I have a 10 mA circuit that I would like to monitor. I'm only interested in the values between 0 V and 3.3 V and only have a 3.3 V supply. But the circuit can end up as high as 18 V. I cannot load the ...
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2answers
73 views

Precision amplitude 600kHz square wave generator

I'm looking for a circuit that creates a precision amplitude square wave of 600kHz (50% duty cycle). The amplitude of the square wave needs to be 3Vpk-pk +/-10mV, but can be DC offset. The output of ...
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0answers
27 views

Opamp: Does the openloop Gain changes depending on the Input stage?

In case for bipolar Input stages on Opamps: does the actucal Openloop gain changes depending on which input stage, n or p channel is used? (which depends on the applied input signal) Could not find ...

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