Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers,

2
votes
2answers
41 views

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

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
46 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
33 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
50 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
82 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
51 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
51 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
39 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
82 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
52 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 ...
-8
votes
0answers
51 views

Please suggest me OP-AMP circuit [closed]

I am connecting a PAM8403 with 2x 3W 4Ohms speakers but the output sound is low. I am connecting power supply for 8403 from raspberry pi GPIO pin and it's input to 3.5mm jack. So I need to know about ...
0
votes
1answer
38 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
78 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 ...
-2
votes
0answers
31 views

Differential amplifier basics

I an differential amplifier whether, inputs are out of phase or outputs or out of phase , Please explain I think the inputs must be in phase to get the difference of each other? Thanks in advance
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
72 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
51 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
87 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 ...
-2
votes
0answers
37 views

Op-Amp comparator or amplifier? capacitor in non inverting input

If someone can clarify to me what is the action of this OP amp, is it comparator or amplifier? I know when there is negative feedback the op-amp is an amplifier, but here has a capacitor, what is it ...
0
votes
1answer
65 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
60 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
296 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
64 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 ...
-3
votes
0answers
32 views

Differential amplifier CMMR, NON-IDEAL Op-Amp used

I have a little trouble with the analysis of a differential amplifier. What I want to do is to determine the CMRR of the whole amplifier taking into consideration the CMRR of the op amp. This is the ...
0
votes
1answer
34 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
88 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
45 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
52 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
53 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
40 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
29 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
69 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
32 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
28 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
113 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
38 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
66 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
104 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
35 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
92 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
83 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
29 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
36 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
59 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
78 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
53 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
42 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 ...