Questions tagged [operational-amplifier]

Questions relating to the construction and applications of operational amplifiers, which are DC-coupled, high-gain electronic voltage amplifiers with a differential input and, usually, a single-ended output.

Filter by
Sorted by
Tagged with
2 votes
1 answer
57 views

Can the corner frequency of thermal noise change with change in source impedance?

In EMG there is a certain level of thermal noise created at the electrode-gel-skin interface which depends on the skin-electrode impedance (also known as source impedance). I have been able get the ...
tilly's user avatar
  • 53
1 vote
3 answers
146 views

High gain op-amp, but still being able to get 0V output

I'm not a learned electrical engineer, so all my knowledge is self-taught and thus a little spotty. I hope you guys can help. Here is my problem: My goal is to switch between ROWPIN 1-4 (there are ...
Victor Mas's user avatar
0 votes
0 answers
27 views

Piezo Transducer RX/RX switch with a charge amplifier

I'm trying to design a circuit that can both transmit a 40kHz square wave and receive a 40kHz sine wave using the same ultrasonic piezo transducer. Switching between them doesn't have to be very fast (...
Michal's user avatar
  • 209
0 votes
1 answer
82 views

Ensuring capacitor doesn't get above certain voltage

I have a circuit here (schematic below) that I've put together, based on US Patent US5439374. The idea is to sense the presence of a flame. I will be breadboarding the circuit before I make a PCB, but ...
Emanuel Elliott's user avatar
4 votes
2 answers
570 views

How can we reduce background noise in this system?

We are experimenting with a glucose test strip (below) in our chemistry lab using an electrochemical method where a potential is applied (150 mV) across the working and reference electrodes and the ...
cucumber's user avatar
2 votes
1 answer
85 views

Essential safety features of an EMG/medical grade device?

EMG consists of an electrode gel skin interface, op-amps with a certain gain and an ADC. Question is in the context of passive electrodes. What are the essential safety features of such types of ...
tilly's user avatar
  • 53
1 vote
1 answer
90 views

What is Ground Electrode in EMG?

*Learning about EMG as a part of our research. My team has at least some experience with electronics that is worth mentioning, but don't have any experience with EMG/bio-potentials. Most EMG hardware ...
tilly's user avatar
  • 53
1 vote
1 answer
67 views

What is the best practice to translate variable resistor 500k to infinity to logic levels?

I have a custom sensor that gives me resistance in the range of 500 kΩ to infinity, I want the 500 kΩ - 1.5 MΩ values to be perceive as a High input in my STM32 controller. Assuming Vin = 3 V and the ...
Chakra41's user avatar
3 votes
1 answer
74 views

What is the purpose of biasing op amp inputs in this Spice model?

This is a two stage amplifier, the first is a high gain charge-sensitive pre-amplifier (U1) followed by a low gain voltage amplifier (U2). A typical charge-sensitive pre-amp for photodiodes has the ...
earl's user avatar
  • 1,105
3 votes
2 answers
284 views

Difference OTA and op-amp

I have a question about OTA (operational transconductance amplifier). Why can an OTA can be used without negative feedback but would still be able to keep its inputs (V+, V-) close each other? I have ...
AnalogMan's user avatar
  • 184
0 votes
0 answers
46 views

Challenges in measuring the output voltage of an H-bridge using an instrumentation amp and resistive divider

Design a circuit that allows me to measure the output voltage of a full H-bridge. Essentially, I'm using a resistive divider for this purpose. The simplified design is as follows: I had issues with ...
WalterPH's user avatar
  • 420
0 votes
2 answers
42 views

Linearizing hyperbolic magnetic Hall sensor response

I am working on a project where I need high precision measurement of distance using a magnet and Hall sensor. The response is similar as in the graph below, meaning that the voltage changes much more ...
Štěpán Dvořáček's user avatar
1 vote
3 answers
128 views

Opamp virtual ground when power is removed

Does the virtual ground condition hold true when I cut off the power supply of the opamp? I am using an opamp as a buffer. If I cut off the power supply but continue to give a signal on the non-...
Rachit Juthani's user avatar
1 vote
2 answers
113 views

Problem with voltage to current converter

I want to get 20 mA output (current) when input is 3.3 V and 0 mA when the input is 0 V. I have tested my circuit but I got about 11 mA when input is 0 V and about 12 mA when input is 3.3 V.
hassan's user avatar
  • 11
2 votes
1 answer
70 views

Introducing RC Filter to reduce noise

I have designed a constant current circuit using an opamp. If I want to implement an RC filter to reduce the noise, where can I add? Option1: I am planning to add between the inverting terminal and ...
Teena's user avatar
  • 101
0 votes
5 answers
187 views

Driving an LED with a P-MOSFET or op-amp as a current limiter and no resistor

I have an application where I need to be able to drive an LED without a resistor. Adding a resistor is not an option. I then must be able to blink the LED on or off by shunting to ground. LED Specs: ...
BobaJFET's user avatar
  • 684
0 votes
0 answers
57 views

Finding memories power dissipation

Can someone tell me how to calculate the power dissipation of digital ICs like NAND Flash, QSPI NOR Flash and microcontrollers?
sushmi Ram's user avatar
0 votes
2 answers
67 views

Is it a good idea to keep large resistors in feedback path of a comparator circuit?

I was seeing a comparator circuit designed with LM2903. The circuit diagram is given below. It is working as expected in simulation. In the feedback path you can see a 1 MΩ resistor. My questions are: ...
Hari's user avatar
  • 1,767
0 votes
1 answer
84 views

Non inverting OP AMP maximum output voltage problem

This is my non inverting OP AMP based amplifier for one of my measuring circuit. I have 2 queries about this circuit: With maximum input voltage of 5 V, I'm getting only 3.7 V only. (I know the ...
Bhushan Waghe's user avatar
4 votes
3 answers
191 views

Fullwave rectifier with active clamp

What is wrong with my simulation? I am simulating with LTspice the following circuit taken from "Art of Electronics 3ed" where my LTspice model looks as follows: What am I doing wrong as ...
abg1984's user avatar
  • 111
1 vote
1 answer
98 views

How can I get the V-I characteristics of negative resistor of Chua diode

I want to simulate the Chua circuit in which a negative resistor is used. I want to simulate the V-I characteristics of Chua diode. But it does not get the same result as shown in book or papers. ...
Usha Kumari's user avatar
2 votes
1 answer
92 views

unfamiliar notch filter configuration [duplicate]

This is a configuration of the notch filter that I saw in some design. It is very different from the Active Twin-T notch filter configs that show up on a quick google search. Any idea what is going on ...
roaibrain's user avatar
  • 199
0 votes
0 answers
59 views

Correct way to think about thermal noise?

I have just started learning about thermal noise in op-amps and while studying could not find if the noise given in op-amps data sheets is random sample to sample regardless of the time interval ...
Joel's user avatar
  • 37
2 votes
1 answer
235 views

LTspice model showing wrong output voltage for op-amp (MP118 - Apex)

I attached my LTspice mode. The amplifier I'm using was downloaded from Apex microtechnology website for MP118. I made necessary connection as per the circuit diagrams I attached. But after running, I ...
Yaser's user avatar
  • 21
0 votes
2 answers
255 views

Audio Mixer Circuit with Individual Volume

I'm trying to make an audio mixer circuit based on the amplifier circuit published by Scott Campbell. I have no knowledge of opamps so I'm taking it mostly as-is but the input signal I am going to ...
SukkoPera's user avatar
  • 191
0 votes
1 answer
154 views

In testing this op-amp, I always get same amplification. Did I break it?

I bought these TL072 (maybe TL072CD) IC amps, for a circuit I was trying to build, but the circuit wasn't working at all so I tried to troubleshoot the amp. I built a voltage divider ~1/1000 (on the ...
Jochen K's user avatar
0 votes
1 answer
66 views

Help identifying a component 1962 solid state op-amp

For my own edification I am reverse engineering a P65A Op-Amp made by Philbrick Research in 1962. I know I could probably find the schematics somewhere but I want to learn, including identifying ...
Integration's user avatar
0 votes
1 answer
56 views

LM311 comparator not working

I have a LM311P which I want to use as a comparator in a different project. To test the working of the comparator I created a simple circuit as shown in the diagram below: As you can see in the ...
RishiC's user avatar
  • 121
0 votes
1 answer
41 views

Voltage controlled resistor at non inverting input of OP-AMP

I am studying a schematics where the non inverting input of an op amp controls what looks to be a voltage controlled resistor (VR202). Without this component, I think the op amp would work as an ...
UnstableDynamics's user avatar
0 votes
1 answer
70 views

module ad620 setup

I am trying to amplify a 200 mV DC signal to single-digit DC volts. I purchased this module. I am struggling to just zero this. I have my 200mV applied across -s and +s. Power to the unit is ...
cucumber's user avatar
4 votes
1 answer
371 views

Fully Differential Amplifier - Stability test Spice circuit

From this post Instability of fully differential op-amp in LTspice, I saw the below circuit for testing stability of Fully Differential op amps : I added the simulation results to show what were the ...
Jess's user avatar
  • 2,970
1 vote
2 answers
107 views

Trans Impedance Amplifier with a photodiode

I made a Trans Impedance Amplifier circuit using a OPA322 op amp with a photodiode (Hamamatsu-S2386). I use a MCP3421 to convert the analogy signal to I2C digital signal after, and use a MCU to read ...
nooblovephysics's user avatar
0 votes
1 answer
139 views

Feedback and opamp

Consider: Attached schematic is from a broken sampling scope that I have in the lab. Cathode of D1 is connected to a sampling gate output, which is sealed in a metal cage. U5 (top right) is the ...
Emm386's user avatar
  • 587
8 votes
7 answers
3k views

Why does this op-amp circuit require a resistor to ground?

The text in section 4.1 of Designing With Opamps - Part 1 reads: Rin is the input resistor, and is needed because an opamp needs a reference voltage at the input. I don't see a similar resistor-to-...
Jeremy's user avatar
  • 81
0 votes
4 answers
111 views

Method of analyzing circuits with diodes and opamps

This is an exercise from an electric circuits course I had on my first semester of university. We are asked to determine the output voltage \$V_o\$ when \$V_\text{in} = 667 \: \text{mV}\$. The diodes ...
Carl's user avatar
  • 3,891
0 votes
0 answers
32 views

Vref circuit design for ADC/DAC

I don't understand calculation and circuit design of external Vref circuits for ADCs/DACs (topic 13.7) in opamps for everyone design reference by Ron Mancini. How to be s=C2R2? How to be determined ...
bb0667's user avatar
  • 115
0 votes
0 answers
38 views

Pipe to Soil Potential Measurement

I want to measure pipe to soil potential using a microcontroller. Generally, the potential difference between pipe to soil is negative. I found this circuit online. Is this circuit correct for ...
Mehedi's user avatar
  • 1
0 votes
2 answers
177 views

Can I amplify a voltage with with a gain around 100 using an op-amp?

I need to amplify a voltage that ranges from 0.049 to 0.059 V to a value of 2 to 5 V. Can this be done using an op-amp? I used this circuit for the design, but while designing I got a negative value ...
Teena's user avatar
  • 101
14 votes
2 answers
653 views

What is the purpose of the positive feedback in this opamp circuit?

Consider: Attached schematic is from a broken sampling scope that I have in the lab. During the reverse engineering the module, I noticed that it uses positive feedback around U2. I understand that ...
Emm386's user avatar
  • 587
0 votes
3 answers
123 views

Connecting oscilloscope probe ground clips to virtual ground

As I have learned, the TT earthing system is primarily used in our country. My power source is an unregulated AC/DC adapter. A transformer and a full bridge rectifier circuit are typically found in ...
user avatar
0 votes
1 answer
58 views

Photodiode and Transimpedance amplifier

I am building a transimpedance amplifier that is connected to a photodiode. (I want to measure the light from a laser). I build one using the opamp LM324N. But it is not working as a TIA amplifier. I ...
Teena's user avatar
  • 101
2 votes
2 answers
140 views

Difference LowPass Filter

These circuits have lowpass circuit. One of these has passive lowpass filter. Another one is active lowpass filter. Both circuits filtered signal for opamp input. Why we have two diiferent circuits? ...
bb0667's user avatar
  • 115
6 votes
2 answers
499 views

Opamp Non inverting Input

I don't understand why this resistor and capacitor are parallel in a noninverting pin in Opamp. Why do we need this circuit? What is the purpose of this circuit? This circuit was taken ADS8555 (pg.33)...
bb0667's user avatar
  • 115
1 vote
0 answers
58 views

What type of control system to use for a ultrasonic cleaner transducer

I got an ultrasonic cleaner transducer that needs 60 W at 40 kHz and I am trying to drive it however since we need amplification I was not sure which board to use. My main question is what is the ...
Shivam's user avatar
  • 11
3 votes
0 answers
71 views

Op-Amp Current Flow through inputs

I am trying to troubleshoot a relatively straightforward op-amp circuit where I am running into unusual behavior where current is flowing into or out of the input terminal of my op-amp. The below ...
Hugoagogo's user avatar
  • 2,415
6 votes
4 answers
1k views

Why is op-amp buffer used at input to ADC?

This is from datasheet of TI part ADS7041: The 200ohm resistor and capacitor form a low pass anti-aliasing filter. On the left of this, we have the input driver buffer op-amp. How do we know if we ...
quantum231's user avatar
  • 11.6k
0 votes
2 answers
119 views

Can all inputs of an op amp be used?

I am asking myself if all inputs (non inverting and inverting ones) can be used. For example, having an LM4562 that has two non inverting inputs and two inverting inputs, with 4 outputs as well, 2 non ...
Nayara's user avatar
  • 5
0 votes
0 answers
29 views

Phototransistor receiver circuit output display 0 V

I am working on a sensor for my university project. The output displays 0 V, but when I put the light in, the value changes. When I put it in the box, it displays 0 V again. I am working with an ...
david mike's user avatar
0 votes
1 answer
84 views

Opamp overheating in analog circuit

I'm fairly new to designing circuit boards. I have built a circuit in EasyEDA that takes a 0-3V3 PWM signal from a Teensy4.1 MCU and converts the signal to 0-20 mA current using a low pass filter and ...
Lukas's user avatar
  • 3
1 vote
0 answers
77 views

Does anyone know what this photodiode circuit is for?

I'm looking at some circuits for some sensitive photodiodes and I'm a little confused about what the following is doing. For context, this is connected between the output of the first stage TI and the ...
LockHarb's user avatar

1
3 4
5
6 7
163