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.
4
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1answer
59 views
Is it ok to power several op amps with the same pair of 9V cells?
I'm experimenting for the first time in the wonderful world of operational amplifiers. I'm processing signals in various ways - amplify, envelope detection, voltage differences, voltage-to-current, ...
2
votes
1answer
68 views
Party-line / Full-duplex intercom - mixing audio signals
Party-line or full-duplex intercoms allow for the simultaneous transmission and reception of audio from all connected stations, i.e. effectively there is an audio 'bus' and each station takes a feed ...
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votes
0answers
39 views
Infra-Red with arduino [closed]
Good Day,
I am trying to build a universal receiver transmitter with an arduino. Basically, I want to understand first how the IR protocol works on normal remotes. Is the signal transmitted modulated ...
2
votes
1answer
41 views
Thermocouple signal conditioning - how to deal with low output swing margin of amplifier?
I have this thermocouple conditioning circuit. Let's say my gain is 100. Minimum low level for AD8237 is 20mV. As K type thermocouple outputs 40uV per 1C, I will have 4mV per 1 degree C.
This ...
5
votes
5answers
156 views
Stability problem in unity-gain opAmp
As a part of a controlled power supply for hardware-in-loop testing for a student driven project, I had to develop a current buffer (voltage follower) which could source up to 1 A.
I had the (bad) ...
2
votes
2answers
102 views
Bipolar Op Amp w/ Near Zero Offset?
My understanding is that if source resistance is low, a bipolar op amp has 10dB less noise than a JFET. I prefer the JFET op amps because the input offset is so low that you can eliminate coupling ...
11
votes
1answer
303 views
Could someone help me understand this simple circuit?
This is a single-wire earth-return telephone system used in cave rescue communications.
simulate this circuit – Schematic created using CircuitLab
The ground is a metal casing to make ...
2
votes
1answer
74 views
LM13700 VCA circuit
I'm trying to build a VCA from the LM137000's datasheet.
The original circuit is with +-15V while I only have a 9V supply. I wonder how the resistor values should be changed so the OTA works with 9V ...
1
vote
2answers
70 views
How to use electrically isolated weak signal for Arduino interrupt?
I'm trying to use the signal generator from a DSO Nano v2 to drive an Arduino interrupt for testing purposes. I have measured the output of the signal generator at approximately 13mA @ 2V DC.
I have ...
-1
votes
2answers
119 views
threshold problem on a Schmitt trigger op amp
I have the Schmitt trigger op amp on the below diagram. (channel A & B refers the oscilloscope probes on the following figures).
The resistor values are selected to set the trigger threshold as ...
6
votes
4answers
171 views
Detect “real” overcurrent/short-circuits vs. current peaks
We have a MOSFET that drives a load. The load has a sense resistor in its current path and its voltage is used to trigger a circuit that can disconnect the load if we detect an over current ...
2
votes
2answers
96 views
Op-amp input stage for Arduino Due ADC - guitar signal
I am trying to design an op-amp input stage to capture a guitar through an ADC, specifically the ADC on an Arduino Due (3.3V, 12 bit). I am aware there are numerous ways to configure and bias the ...
0
votes
1answer
97 views
Does a capacitor in an inverting op-amp make a difference?
Just a quick question, does a capacitor in an inverting op-amp make a difference to the transfer function? Or, are just the resistors taken into consideration?
Non-Inverting op-amp:
\$ \dfrac{R1 + ...
1
vote
1answer
128 views
Integrator and differentiator - op-amps vs. RC networks
Integrator and differentiator circuits can be made using an op-amp:
and a simple RC network:.
Is one better than the other? What are the differences between the two, if any?
1
vote
2answers
104 views
Circuit analysis of mono audio preamp (K1803 Velleman)
For a school project I have a question about the first part of the circuit below (amplifies at 20*log(220k/2.2k)=40dB). I know that U2A is the amplifying part of the circuit. The problem is U1A and ...
1
vote
1answer
75 views
increasing output voltage of a schmitt trigger op amp
I have the Schmitt trigger circuit below that I read the output as 1.6V for the logic High. I wonder how can I increase the output voltage of the comparator below without changing the threshold of the ...
5
votes
3answers
204 views
op-amp vs direct control
I'm experimenting with small motors (just building useless toys so far) and I'm wondering what benefit there would be to using an op-amp to control a motor (top circuit) vs just controlling the motor ...
-1
votes
1answer
108 views
non-inverting schmitt trigger op amp - replacing a zener diode on the input
I wonder if it is possible to replace the second figure below with the first one? Would both Vo output be the same on the figures below? If they are different, ...
0
votes
0answers
41 views
Loading effect problem
i m trying to connect a de sauty's bridge(AC bridge) output to a precision rectifier. The problem is the output of the bridge (AC bridge) changes drastically to 5volts as soon as the connection is ...
1
vote
1answer
69 views
Twin T circuit noisy
I've been fiddling with a twin-T percussion oscillator with success. It's built on a breadboard and it sounds exactly how it should sound (damped sine wave, big 808/909-kind of kicks). However it's ...
2
votes
1answer
162 views
Voltage regulator with op amp(negative feedback) and MOSFET
The schematic above is a very good voltage regulator, excepting the high power dissipation for Q1 (also I'd use an NPN instead of a PNP). Can I replace Q1 and Q2 with a high current n-mosfet and ...
1
vote
3answers
92 views
Economical thermocouple amplifier circuit
I'm looking for the most economical circuit that reasonably accurate circuit for amplifying the voltage produced by a thermocouple (so it can be read by an ADC). For the sake of argument, component ...
-1
votes
4answers
129 views
If-else decision structure using op amps or any other non-programmable electronic device
The title is pretty clear, I would like to know if there is any circuit or an IC capable of dealing with signals to perform algorithmic sort of decisions, I mean, as you can solve differential ...
2
votes
1answer
118 views
Trouble transferring schematic (working) to actual circuit (not working)
EDIT: At this point I'm just going to implement it in software. I give up. :< Thanks though!
So I keep screwing up this circuit, and the simulation works just fine.
The simulated circuit: ...
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votes
0answers
51 views
Measuring voltage change between two separate circuits [closed]
Is it possible to measure a voltage produced from one circuit in another which is powered by a different cell / power source.
To give a simple example, is it possible to have a potential divider on ...
3
votes
3answers
140 views
How to electronically generate exponential and logarithmic functions
i mean, it is possible to generate with Op amps, or diodes, etc, to generate complex exponential and logarithmic functions, like one can create sinusoidal signals using a Wien bridge oscillator.
...
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votes
1answer
258 views
Op Amp based Colpitts oscillator
I have designed an op-amp based Colpitts oscillator in multisim. When I press run button it shows- "timestep too smaall error". I've googled and tried everything but it still shows the error.
The ...
3
votes
1answer
149 views
Constant current source math - Using AD8276 differential Op-Amp
So I'm trying to implement a constant current source to conduct a specific measurement using a
AD8276 differential amplifier. I'm trying got derive the equations my self for sanity check, and to give ...
3
votes
3answers
84 views
Inverting Op Amp question
I'm having trouble with this particular inverting Op Amp question.
I know that there are 2 nodes and I must apply KCL on the nodes.
What I tried was ...
0
votes
1answer
261 views
Feedback for DC Motor Speed Control using PID
I'm working on a project in which I have to control the speed of a DC motor using an analog PID(using op-amps). The input will be provided with a potentiometer. The issue is that I can't figure out ...
5
votes
4answers
320 views
Why does this current limiter circuit oscillate?
I'm trying to make a 0-25 mA current limiter. I want to take a control voltage of 0-5 V as input and have it control a current of 0-25 mA through a restive load (the restive load may vary between ...
1
vote
1answer
97 views
Problem with microphone powering up a comparator circuit
The circuit below is supposed to turn on a LED when the microphone input reaches these levels:
1V, 3V, 5V, 7V.
What this circuit does in real life is when we turn on the power, all 4 LEDs light up.
...
1
vote
2answers
98 views
Tips for adding voltage op amp to equipment
I have a source that creates a smooth sine wave in the range ±100mV at 1-15Hz.
Due to distances I need to amplify the signal to at least ±5V, and I should also maintain the shape of the signal if ...
3
votes
4answers
343 views
What is the use of analog circuits today?
While studying analog circuits and conducting experiments with op-amps, I couldn't help wondering why would I need an analog circuit to add/multiply/integrate electrical signals. In modern times, ...
1
vote
2answers
124 views
How to justify that op-amp 1 has negative feedback?
Op-amp 1 is topmost in the schematic below. I used the ideal amplifier method (using A until the end and then lim A->infinity) and also the virtual short method.
But I don't know if that's enough to ...
0
votes
1answer
100 views
Transimpedance Amplifier: Silly question that's killing me
I'm having huge trouble with this problem, I've probably done it 10 times already and there must be something that's slipping my attention.
The givens are:
\$I_{PMT}\$ = 150.0 pA, R1 = 73.0 MΩ, R2 = ...
5
votes
4answers
283 views
A probably very easy Op-Amp Analysis
simulate this circuit – Schematic created using CircuitLab
Original schematic
Could anyone offer some insight on how to solve this circuit? What I've been doing so far, is only producing ...
2
votes
5answers
111 views
Flow of current in a simple inverting amplifier circuit
I am considering a simple circuit like the one below. Let us say that the voltage source suddenly turns on (from 0V to 1V), then current will through through the resistor R1, correct? But assuming ...
1
vote
1answer
92 views
Find Vo in an op-amp - transistor circuit
I have a schematic with this system and can't find out how it works:
simulate this circuit – Schematic created using CircuitLab
How do I find Vo in this network? Please explain it "for ...
4
votes
3answers
238 views
Solving this op-amp circuit
I would appreciate some help solving the following circuit. I've been trying for a very long time and can't get the same answer the book has. I'm trying to get \$ V_o \$ in terms of \$ I_{os} \$.
...
1
vote
3answers
136 views
Op amp picks up power rail oscillations from boost conveter
I've built a circuit which detects ambient audio through an electret microphone, amplifies the audio signal using a LM386 op amp (gain = 200), and then processes that audio information. The board is ...
6
votes
5answers
226 views
OP amps with output on N-channel MOSFET
I need to analyze a schematic and I am having trouble with this part:
The thing is I don't get at all the utility of the N-channel MOSFET at the output of the op-amp. Could anyone explain the ...
1
vote
2answers
162 views
transfer function of active filters
I've been looking for some straightforward method or trick to obtain the transfer functions of active filters (like the Sallen-Key filter , the butterworth or Cauer topology etc...) since KCL or KVL ...
0
votes
1answer
242 views
Amplifying Low DC Voltage Consistantly
I'm looking to build an amplifier circuit to amplify a small DC voltage signal (between 0-15mV) to the range of 0-1.3V. I tried messing around with a standard non-inverting op-amp amplifier circuit ...
5
votes
1answer
106 views
How can I lower output impedance of an accelerometer?
I'm planning to use an accelerometer with a microcontroller to measure acceleration. The issue that I have ran across is that in PIC microncontrollers the ADC requires that the connected analog ...
-3
votes
1answer
95 views
How RL affects gain in non-inverting op amp
I need to know if RL affects the gain of a non-inverting op-amp? I have a non-inverting op amp with a feedback 50kohm resistor and a 1k ohm resistor to ground. At Vout, I have 3 separate load ...
1
vote
3answers
134 views
Stereo AM/FM Concept?
There are tons of schematics and concepts online of AM or FM transmitters. I wish to build one using discrete components (at most an op-amp).
The problem is, how would transmission of stereo work? In ...
2
votes
2answers
143 views
Treble Bass Op Amp
Good Day,
Can I know how bass and treble can be controlled using an op-amp? I have googled for several solutions but it shows some really complex designs which I don't get.
From my understanding, an ...
0
votes
1answer
101 views
Relationship between the circuit bandwidth and the gain for an inverter op amp
do you know the relationship between those two quantities, for an inverter configuration of the op amp. I know graphs, but i do not know any equation or function that relates those two quantities.
0
votes
1answer
79 views
Degradation of AC signals as inputs of inverter amplifier circuit
i recently, did a configuration of an inverter op amp model and i fed it with an analog signal of the form$$S(t)=2sin(1000t\pi)$$
As you may know, the general response of an inverter Op Amp (741), is ...
