Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers,

Filter by
Sorted by
Tagged with
2
votes
2answers
53 views

Need help finding a high voltage, high slew rate Op-Amp [closed]

I am designing a single stage driver circuit that needs to be capable of driving a rectangular pulse wave up to voltages of +50V. The slew rate has to be at least 500 V/μs. So far, I have found 2 op ...
0
votes
1answer
50 views

Which Comparator could match this electronic circuit?

Below is a schematic of a current regulator using a comparator IC2. The board is from an XP-605 ELENCO bench top adjustable power supply. Searching the WEB was unsuccessful in finding any original ...
1
vote
1answer
41 views

Current source for high current LED driver- 24Vdc/max:16A

I am working on designing a current source for a LED driver, which can work up to max:16A, as long as stays On less than 500msec. Actually, the leds circutry is a Dome-light which is divided in 4 ...
0
votes
1answer
59 views

How to avoid the saturation of the current amplifier?

I have to calculate current gain of the following circuit and to model it in Spice. I arbitrarily set Is = 0.0002 A: Here are the results provided by LTSpice: Also, in order to find an equation for ...
0
votes
1answer
99 views

Noisy op amp buffer

I made an op amp buffer using a TL071 for my guitar but it is very noisy. The circuit is a simple follower. Originally I had no feedback resistor but I added it later in case it decreased the noise ...
0
votes
0answers
53 views

Derivative amplifier

I want to handle 8 and more buttons or switches with only a few MCU pins and receive interrupt whenever some of the buttons is pressed (even if some switches are active). I'd like to use PISO shift ...
0
votes
2answers
69 views

What's the voltage transfer characteristic of this power driver circuit?

[Exam problem for an instrumentation course] Can anyone help me understand how this circuit works? I'm not too familiar with power circuits... This somewhat reminds of a BJT class B amplifier (but ...
0
votes
1answer
44 views

How to select resistance to cancel offset output voltage due to bias current?

Consider the figure above how Rcomp was choosen. I know for simpler circuits like inverting amplifier and ideal integrator how Rcomp was calculated but following same procedure (that's using ...
1
vote
3answers
95 views

How to find input impedance of this OPAMP circuit?

Assume OPAMP to be ideal with infinite gain (a) and infinite input impedance I am clearly able to see that the input impedance of this circuit is R1 (correct me if I am wrong) but I am unable too ...
0
votes
1answer
95 views

Test cases for for OTA in LTSpice

Here is a component OTA provided by LTSpice which has inverting non inverting common and output node. I am in process of modelling this OTA behavior form LTSpice to PSpice. I reffered this link for ...
0
votes
1answer
48 views

Wheatstone bridge and difference op-amp

I use Wheatstone bridge as a dual voltage divider to feed both inverting and non-inverting inputs of differential op-amp: Theoretically voltage can be calculated using voltage divider expression: Va =...
1
vote
1answer
101 views

Photodiode showing triangle waves instead of square? (re: need op amp?)

I'm trying to visualize an infrared signal using a IR receiver diode but my oscilloscope is showing triangle waves instead of square for the carrier frequency: One of the guys at EEVblog said I need ...
0
votes
1answer
34 views

Direct coupling Biasing of Two stage amp

General question. I see a lot of two stage amplifiers with a diff pair input and a cs second stage. In IC design these two stages are always directly coupled ie. the dc bias of the second stage is fed ...
3
votes
1answer
76 views

Resistance between non-inverting input of op-amp and voltage source

I encounter quite often this sort of problem in my textbook: This is a classical non-inverting op-amp. However, I'm always perplexed with resistance R1 between voltage source and non-inverting input. ...
1
vote
1answer
56 views

Laser audio transmitter - need substitutes

I'm building a laser audio transmitter that uses amplitude modulation to transmit audio via a 5mW laser beam. The transmitter uses a microphone, an operational amplifier (to modulate the signal if I'...
0
votes
2answers
107 views

Can I use a simple voltage divider with an instrumentation amplifier to measure from 0 to 10V?

There is a design of a circuit proposed in the following way: simulate this circuit – Schematic created using CircuitLab The amplifier has a gain of 80, on R1 when the input voltage is equal ...
0
votes
1answer
66 views

What kind of op amp is it? how do I calculate the VA voltage?

the first value of Q1='0' (off). how can I calculate VA voltage, the output of op amp ? I am not sure if is it like a buffer cause I've never seen some buffer like this. thanks ahead for any help ...
0
votes
3answers
64 views

When to put resistor on comparator input

I am using a open-collector output comparator (ROHM BA8391G) to enable a voltage regulator when Vin > 12V is detected (comparator output will be HIGH when Vin > 12VDC). Vin can be in the range of 12-...
3
votes
3answers
303 views

Can an opamp have its own voltage regulator?

I'm wondering if we use batteries instead of stable power supply for the opamp power rails what would be the consequences. If we use an opamp for precision application would using batteries a bad ...
1
vote
1answer
71 views

Detecting “quick falls” in signal

I am conditioning the input of a slowly drifting analog input sensor. The sensor is a phototransistor that will sink a small amount of current when "dark" and 50x more current when "bright," but the ...
0
votes
1answer
44 views

summing amp - floating inputs

I'm designing an audio mixer and currently i'm working on a cue section. The whole point is that i have 2 or more channels and want to mix them in summing mixer. You can turn off the channels you don'...
0
votes
1answer
27 views

What is the predictable difference of the voltage drop between the V+ and V- lines on a shunt resistor?

I am making an electronic speed controller, and the half-bridge driver I am using has a built-in overcurrent protection feature. In order to utilize this feature, I have to supply the pin (a ...
0
votes
2answers
94 views

How to scale down voltage of the the video signal without affecting input wire impedance

This is a question stemming from this one where I search for the root cause of AD725 displaying wrong colors. Current step have shown that I must be out of the spec for the input of the chip: my RGB ...
3
votes
0answers
54 views

PIN Photodiode gamma detection amplifier circuit - rectangular wave output

I've been working on a project recently, where I need to build a device which detects gamma radiation and can be used for gamma spectroscopy. I've done some research and found many interesting ways of ...
1
vote
2answers
58 views

Transimpedance amplifier calculating feedback capacitor

What is the correct way to calculate \$C_F\$ of the transimpedance amplifier? Since I have two different documents, each has a different way to calculate it. Base on these two documents: 1. Maxim ...
2
votes
1answer
59 views

Op amp circuit with two capacitors

Based on an electronics lecture, we are dealing now with the preamplifier circuit for a detector. The figure is shown below. Actual I am having the problem to understand the center operational ...
2
votes
1answer
45 views

How op-amp stabilizes?

I have a problem understanding one thing in op-amps, namely - when the cycle of stabilizing ends? For example, when we have simple non-inverting amplifier, firstly the difference equals the amount of ...
5
votes
2answers
2k views

Rail-to-rail op-amp only reaches 90% of VCC, works sometimes, not everytime

I have created a simple data acquisition module for measuring 5V signals. There are 18 analog inputs on this board, all of which are a copy of the schematic below. Each input has an op-amp (MCP604) ...
0
votes
1answer
36 views

Measuring AC signals from sensors

I have a non invasive current sensor SCT 013-030 and I connected it to an AVR mcu using this circuit below (circuit 1). Circuit 1. simulate this circuit – Schematic created using CircuitLab ...
2
votes
1answer
74 views

Transfer function of a summing integrator

I'm trying to derive the transfer function of a summing integrator for use in a feedback circuit. The single input and double input integrators are shown below. An integrator with one input is ...
0
votes
1answer
35 views

How do I find this value for the feedback fraction?

How exactly do I find this value for the feedback fraction Beta? Thank you. omega_0 here is the natural frequency calculated as omega_0 = 1/RC and s is the complex frequency.
0
votes
1answer
31 views

Why is the gain of an integrator built using op-amp -Rf/R1 till cut-off frequency

As you can see the gain is constant for the practical op-amp, even though gain is This shows that it clearly changes for every frequency. Is the one in the graph an approximation, maybe because it ...
14
votes
4answers
2k views

Active low-pass filters — good to what frequencies?

Appendix E of The Art of Electronics, 3rd Edition (LC Butterworth filters) starts by saying that "active filters are convenient at low-frequencies but impractical at higher frequencies". They go and ...
2
votes
2answers
115 views

Operational Amplifier Problem

I'm trying to find $$\frac{V2}{V1}$$ as a function of x. I found this circuit but noone gave good explanation. I think I understand the way this potentiometer works, but I just can't work out the ...
0
votes
1answer
41 views

Triangle generator circuit - supply rail error

I have a simple triangle generator circuit soldered and powered by 5V rails shown below. Verified by simulation and equations, it should output a 500kHz triangle wave a \$\pm4.2V\$. Instead, the only ...
1
vote
1answer
68 views

How do I know if this is a positive or negative feedback to the op-amp? [duplicate]

I am trying to build a line-following robot with the schematics I found below. I have just started to understand the use of feedback in op-amp. Ie. The continuous balancing mechanism creates a very ...
0
votes
1answer
109 views

Is the op-amp inverting or non-inverting?

I am studying the function and characteristic of an op-amp to build a line-following robot with the schematics below. However, in many tutorials, the way to differentiate an inverting and non-...
0
votes
0answers
40 views

Troubleshooting op-amp circuit and compactor for buzzer

I tried building a radiation detector (cheap photodiode Geiger counter) on perfboard: http://opengeiger.de/StuttgarterGeigerleThruHole_en.pdf More details here. With the circuit was turned on, ...
0
votes
4answers
93 views

non-inverting op-amp with reference voltage on negative feedback?

Hi, I am having a lot of trouble understanding this configuration. When i first saw it, it thought that the 2.5V reference voltage would force 1.25V on the negative terminal but after opening it up ...
3
votes
1answer
92 views

What is this Venn-Diagram-looking symbol?

So I am looking at the datasheet for the LTC4416, and there is this Venn-diagram symbol after the op-amp, but I don't think it is supposed to be an inverter. It is also used for these currents, but ...
1
vote
1answer
35 views

Analysing AC-Coupling differential opamp configuration

I built an audio DSP board based on CS4272 and used its reference design for the output section. The signal is getting extremely distorted when summed signal exceeds ~0.7Vpp. (Rail voltages 0V-5V and ...
1
vote
1answer
41 views

How to calculate the maximum amplification of a transimpedance amplifier

I want to calculate the maximum amplification that I can get out of my transimpedance amplifier and I'm struggling a little bit with how to do determine this value. Is the amplification simply the ...
0
votes
3answers
68 views

How is this servo amplifier made work in SPICE?

At page 13 of this Analog Devices document there is a circuit which consists of a servo amplifier and a bridge. The operation principle is explained in the document. Here is the the schematics given: ...
-1
votes
3answers
82 views

Op-amp: Virtual ground principle and other doubts [closed]

I can't understand some stuff about op-amps. Here is my list of doubts: If an op-amp amplify the difference between the V+ and the V-, how can it work if for the principle of virtual ground V+ = V-, ...
0
votes
1answer
54 views

DC Voltage Comparator

I'm looking to build a simple DC voltage comparison circuit that outputs a logic high or low depending on the input, say when it rises above 2V. From my admittedly rudimentary understanding of op-...
0
votes
0answers
43 views

micro controller cant able to sense analog value (ADC input) from op amp output

I am trying to sense the current in my motor controller using shunt resistor and an op amp. Opp amp amplifies the voltage drop of the shunt resistor, multi meter shows the output voltage good. But ...
2
votes
2answers
71 views

Double wave precision rectifier frequency response

To perform a didactic experience, I had to design a double wave rectifier by using op-amps (TL081). I choose to use two stages: a single wave precision rectifier (i.e. ideal diode) and an inverting ...
-1
votes
2answers
114 views

Analysis of this analog mux circuit

I would love an analysis of this circuit, as I suspect the mux is trying to digitally adjust the gain of the amplifier. But what is it adjusting, current gain or voltage gain? And how?
1
vote
3answers
68 views

Modification on a sine wave before ADC

I actually have an Arduino Due board, with everything working on it, using the ADC and the DAC. For my input for the ADC I need to have a signal 0-2.2V but my signal is actually between -5V to +5V. ...
0
votes
2answers
64 views

Increase gain reduction on op amp filter

The image below features the EQ section of a DJ mixer with -26db gain reduction on each frequency band (hi/mid/low). My goal is to modify this circuit so that the op amp filters are "full kill" (aka ...