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Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers,

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24 views

Inferior limit of output voltage in op-amp low-pass inverting amplifier circuit

I'm simulating the low-pass inverting amplifier circuit using LTSpice: I put a sine of amplitude 4 as input to see the behaviour of the op-amp in the non-linear zone. I was taught that the output ...
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1answer
51 views

Is it possible to measure phase margin with the loop closed?

Everything I read on the web, concerning this question, says that in order to measure or set the phase margin of an amplifier the loop must be opened and the phase lag around the loop measured when ...
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0answers
28 views

how would a non inverting op amp tone boost work?

I'm modifying an audio circuit to add more tone controls, and found a method I want to try. It involves separating the wanted frequencies into a boost circuit and the less wanted frequencies around ...
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2answers
59 views

Full wave rectification by opamp

I am trying to read a current waveform from a shunt resistor series with the power line. Using a full bridge rectifier, I got the following waveform: The waveform was sampled every 2 millisecond ...
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1answer
34 views

Adjusting the gain on a 4th Order Butterworth Bandpass fIlter gain

I designed a bandpass filter with the TI filter designer tool but I initially designed with a gain of 40 dB. However, I'd like to reduce the gain to 20dB but I'm having issues doing trying to figure ...
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2answers
70 views

How to analysis this Operational-Amplifier circuit?

This is a reference buffer circuit that make a single-end audio input to be the differential inputs for ADC. Circuit-1: It does not like typical Op-Amp circuit of the same purpose like below. ...
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1answer
38 views

Lower noise in biased op amp

I have a circuit similar to this. I’m trying to lower my noise under 60 Hz. Using pspice I keep finding that I need a very large resistor for R5, like 50 gigs but in practice this is not giving me the ...
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3answers
37 views

Interrupt generating circuit: 0 ~ +3.3 V

For the purpose of testing a MCU and it's interrupt handling I want to design a circuit to generate interrupts. Ideally I would use a relaxation oscillator, but my supply is constrained to 0V and +3....
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1answer
64 views

Calculate right leg drive integrator

My question intersects with "What does this op-amp circuit do? (part of an ECG)", but I need some more detailed clarification on the opamp integrator of this right leg drive circuit as found in the ...
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1answer
54 views

Searching for an Op Amp which amplifies an input voltage of 3mv to say +-5v [on hold]

It would be really helpful if someone suggests an Op Amp which takes an input voltage in mV and the output of +-5v. If there's an evaluation board that comes with the Op amp which takes the mv input ...
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2answers
58 views

Is the following op-amp-circuit-in-the-Laplace-domain analysis correct?

I am relatively new to analyze circuits in the Laplace domain. So I decided to solve some problems as an exercise. Below presented a problem and my solution to it and I have two questions: ...
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0answers
45 views

What component is best for a voltage follower amp (specs given in question)?

I am wanting an op amp that can act as a voltage follower. Essentially the project is speed control of a motor and since PWM is being used, the following circuit was going to be implemented: ...
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2answers
52 views

Inverting OpAmp non-symmetric output

I've got the attached circuit and layout setup - basic signal conditioning going into an ADC. First we buffer the signal with a unity gain follower. I can verify with the scope that the output at TP2 ...
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1answer
36 views

Multiple Analog input for one channel ADC with Amplifier drivers?

I have a concept of using a one channel ADC for three differents analog inputs sources. My question is: should I worry if the the analog inputs have differents inputs impedance, one is very high ...
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3answers
84 views

Using Op-Amp to amplify DC?

In all the textbooks the shown inputs to Op-Amps are AC. Could one use Op-Amp to amplify a DC voltage? if the answer is no, why not? Why only transistors can be used to amplify DC, aren't Op-Amps ...
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2answers
375 views

Will love to understand how the circuit works based on this schematics [closed]

Just a pure understanding of the workability of this circuit.
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1answer
46 views

40kHz Ultrasonic transducer - datasheet gives capacitive load at 1kHz what is it at 40kHz?

A hopefully simple question, the datasheet for a 25kHz Ultrasonic transducer gives the capacitance load at 1kHz what is it at 25kHz? I've been calculating the current using I = fCVpp where f is ...
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2answers
83 views

Offsetting Voltage from 2.5 V to 0 V without Effecting gain

I'm trying to digitize a Hall Sensor whose center voltage is 2.5V and the gain it's output is 1.5V to 3.5V, or ±1V. My digitizing card's center voltage is 0V and I would like to get the full range of ...
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1answer
46 views

Inverting OP AMP SLEW RATE

I'm trying to do a question that requires me to design an inverting op-amp in multisim and find the slew rates in different scenarios using the OPAMP_5T_VIRTUAL operational amplifier model found in ...
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3answers
81 views

How to add a low pass filter to this non-inverting amplifier circuit?

I've come up with this simple circuit as an amplifier before an 8bit ADC which receives audio signals. R2 is actually a variable resistor (pot.) of 100k. The circuit also biases the signal to VCC/2 ...
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1answer
48 views

Feedback Circuit schematic to Control Theory block diagram?

I'm studying analog electronics circuit with feedback. I see that, during analysis, a useful abstraction over the schematic is the block diagram in control theory style, but I stuggle in deriving it ...
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2answers
85 views

How to design voltage gain circuit?

I need to build a circuit with a DC gain of 2 for a 0-5V input, 0-10 V ouput (input will be adjustable). Current can be low since it doesn't really matter (this will be purely as a control signal). ...
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1answer
96 views

differential and inverting op amp problems

I am trying to offset a triangle signal of 4 volts peak to peak by around 10.2V up with only a +20 volt supply voltage, I do it using a differential amplifier but the output signal is inverted so I ...
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1answer
45 views

How to amplify a signal for piezo transducer from 1 Vpp to 200 Vpp at 400 kHz and 500 pF load

I'm a researcher working with phased ultrasonic transducer arrays. I need to amplify a sine wave at 400 kHz and 1 Vpp to 200 Vpp. It has a capacitive load of 500 pF. I'm little ...
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0answers
37 views

Error converting PSPICE model for LT Spice

I'm using LTspice XVII, and I'm having issues generating components from PSPICE component files. Previously, I was able to follow the method of opening the netlist file, highlighting the name, right ...
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4answers
77 views

Negative feedback and op-amp poles

I'm trying to get a better understanding of frequency compensation for op-amps. I'll start off with a very specific questions and then get into the context. For a certain op-amp, open loop gain is ...
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2answers
52 views

Bode diagram calculating for random frequency

The max Gain of an opamp is 100dB (=100000). I have a cutting frequency at 10 Hz and then the slope of my bode diagram decrease by -20dB/dec . I have unity gain at 1MHz. For 100 Hz its increasing by ...
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4answers
153 views

Diodes in an op-amp feedback

Consider the following circuit: (notice the 20 diodes in the feedback loop). If I analysed this correctly, the output from the common-emitter amplifier is just the input signal but inverted and with ...
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0answers
43 views

Single-ended to differential audio preamplifier for low impedance power amplifier [closed]

I'm searching for a suitable IC solution to handle four audio 4V single-ended input signals and get for each of them, a differential output signal (with the possibility to have a gain) to drive an OEM ...
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3answers
66 views

Flat line on output of single supply sawtooth generator

I have built the following sawtooth generator using LM358 opamps: In simulation everything works fine, however in reality I get only flat line on output. Anyone got any idea what's going on?
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1answer
42 views

Compensated vs uncompensated Op Amps [closed]

What are the advantages/disadvantages of compensated and uncompensated op amps? Thank you in advance.
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3answers
74 views

Difference between two integrator circuits

What is the difference between the two integrator circuits? They are used in an amplifier with feedback. There's heaps of information online about the one on the right but not so much about the one on ...
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0answers
29 views

Can I amplify a thermocouple Signal with the GS8332-SR OP-Amp?

Theremocouples have a very small voltage of around 0.4mV/10C. K Type Thermocouple Voltage Table I want to amplify that signal so I can read it with an ADC on my Arduino Microcontroller. The Voltage ...
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1answer
70 views

How to protect OpAmp output from short circuit to +Vcc?

I am using an OpAmp to amplify an input signal that ranges from 0-3.3V to a 0-5V range. The output must only be greater than 0 if the input signal is as well. If I understand it correctly, if +Vcc ...
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1answer
56 views

Reference voltage changes when connected to inverting input of op amp comparator

The capacitor C2 keeps the value of a slow varying signal for some time. The capacitor discharges through the two resistors R3 and R4 with a time constant of \$\tau = RC = 10\mu F \times 1M\Omega = ...
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0answers
41 views

Excessive Op-Amp Settling in Exponential Converter

This circuit converts a linear voltage to exponential current for controlling the frequency of a VCO. It simulates without issues, and almost works, but there is a huge amount of settling on the ...
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2answers
156 views

Gain of Non-Inverting Amplifier Does Not vary with Resistor Values

I am trying to build a non-inverting amplifier using a LM7171 op amp, and I am implementing it with potentiometers as Rf and R2 so that I can smoothly control the gain of the amplifier (and easily ...
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1answer
51 views

How to DC bias op amp?

I'm trying to bias an op amp, I'm reading this document for reference. I'm reading along and it makes perfect sense until section "How to Select Component Values:" They want to amplify a signal ...
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1answer
35 views

What is the difference between differential rail-to-rail, push-pull rail-to-rail and rail-to-rail OPAMPs

I'm loking for an rail-to-rail OPAMP to my project. I need a OPAMP that fed by a 12V and a -5V power supplies can generate an output voltage near these values, at least, near the positive 12V, the ...
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3answers
65 views

Understanding negative feedback in an inverting op-amp

Below is a basic inverting op amp. I'm having trouble seeing the negative feedback operation. simulate this circuit – Schematic created using CircuitLab If I understand the "golden rules" of ...
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2answers
58 views

Comparator as a current detector

I'm looking for a simple circuit that uses only a comparator (or an opamp) to detect the presence of a small current through a high-side current resistor. The idea is for a microcontroller input to go ...
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1answer
66 views

Preventing op-amp output fluctuation at power-off event

What methods exist to place the outputs of an op-amp in a fixed state when power is removed? I have a circuit that uses an LM324 to process an analog input signal. As shown below, the input signal ...
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2answers
61 views

Finding the negative feedback loop in the amplifier circuit

Today I was learning about the negative feedback in the amplifier circuits and some quick ways of discovering whether a negative or a positive feedback exist in the circuit by finding a feedback loop ...
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1answer
68 views

Cascading Op Amps for Phototransistor Output Conditioning

I am working on a project in which I am using an IR phototransistor to detect changing low levels of light. Currently with very high load resistance I can get a reading of 40-60 mV but I would like to ...
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0answers
39 views

How to get the AC analysis result from this non-inverting amplifier with capacitive feedback

all! I have no idea for how to get the AC analysis result from the below circuit. although, I have already known the right answer from textbook as below: Can anyone show me the proof step by step?
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2answers
1k views

Single supply non-inverting amplifier using op amp

I'm working on building a distortion guitar effect pedal for an analog electronics class I'm taking. I am struggling with building an amplifying circuit using an op amp (we just began learning about ...
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4answers
92 views

Opamp output to source and to sink

The output impedance of an ideal opamp is zero. The output of an ideal opamp acts as an ideal voltage source. The output of the opamp should be able to output very large currents (to source) and (to ...
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32 views

Irradiance sensor circuit

Im trying to measure the irradiance from the sun using the following TIA circuit: I'm using a BPW34 photodiode due to the good spectral range and for being cheap. Also the datasheet provides a ...
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1answer
50 views

Input impedance of differential amplifier

Can someone please explain to me, how I should look at the input impedance of the opamps, seen through the voltage \$V_1 V_2\$? I have two questions on the differential amplifier: Why doesn't the ...
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0answers
22 views

How is trigger initially higher than vcc/3 in 555 monostable timer?

I get that the trigger must be lower than vcc/3 in order for the comparator to show '1'. But initially how is the trigger higher than vcc/3? In some text it says trigger is initially vcc and so ...