Op-Amps Interview Questions 

? i have a project where i have 4 LED lights. i need each LED to come on or activate at its respected voltage. I.E, LED 1 comes on at 3v and 3v ony, LED 2 come on at 4V and 4v only ect........
i have thought about using AND gates, op-amp lm324, resistors, rely swichts, and ciruit brakers. the only thing with them ideas is that its going to make it that much harder, i know that its a easier way to do this, i feel it, i just need a lit help, what you think?? what can i build or buy that can tell the differents between what volts is being apply and only let though its set voltage. thanks a lot. every though is needed

##Description of the circuit.
The circuit was made up with 12 ICs (LM324 op amp) and 24 1kOhm resistors (voltage divider rule) and a 10kOhm (to cancel the noise), 1 3k Ohm resistor(if not the 12th Led will be lighting up at 11.1 V instead of the desired 11.9V), 12 LEDs (4 green, 4 yellow, and 4 red) for all the respective voltage level. (1-12V)

##Problems
The circuit works great and now i have a problem writing a report of it. What should i write?

1) I was asked to run tests on the circuit but i dont know what sort of test should i run on it.

2) and i was asked to take photos of the circuit while i'll be passing up the circuit along with the report to the lecturer. So what sort of pics should i take and print on the report?

please help as this is the first time i write reports for this!
THANKS!

We used 741 op amp, and we have the basic differential amplifier which we wired. The values are
Rf = 15kOhm (connected at inverting terminal and pin6)and Ra = 5kOhm (connected at inverting terminal )
Rb = 5kOhm (connected at non inverting terminal )Rc=15KOhm (connected at non inverting terminal and grounded)
Vcc = +15V (at pin7)
Vee = -15V (at pin4)
Channel 2 of oscilloscope is set to 2volts/div and connected to output (pin6). Channel 1 also set to 2V/div is connected to pt.a

The output waveform clamped down by 1V.
What is the explanation of this case?

Also, when we replace Vb with Vc, the ac signal clamped up now by 2V.
why is this so?
What happens when as ac signal is added or subtracted to a dc signal???

Sorry for so many questions, but please anyone help me on this problem...
Please dont hesitate to share whatever you know about this,
it might help me a lot!
MUCH THANKS IN ADVANCE!!!

i have to some project for this subject..but still didnt know which topic is better..my lecturer ask me to build a simple circuit/system that will make use at least one of these electronic elements -

Op-amp
Feedback system
Voltage regulator
Oscillator
555 Timer
Power amplifier

the project must include this criteria
1) Introduction/Abstract
2) Objective
3) List of the components used
4) Circuit ( graphic diagram or block diagram)
5) Explanation of the system (circuit operation)
6) Results (calculations, simulations and etc.)
7) Discussion & Conclusion
8) References

so,i just need an idea which topic is better and where the link that i can refer to..all your kindness will appreciate..thanks..

a postive feedback op-amp with resistance r4...r1,v1 at invertnig terminal and r3,v3at inverting terminal........r2,v2 at non inverting terminal....calculate v0 in terms of a1v1+a2v2+a3v3...............a1=?,a2=?,a...

I'm trying to build a little audio amplifier circuit, and it doesn't seem to be working. Here's the circuit:

http://img242.imageshack.us/my.php?image...

Specifically what I'm wondering about is the electolytic capacitor on the output pin of the op-amp. Is that the right thing to do? Using my multimeter I've figured out that the voltage going into the capacitor is nice and amplified, but coming out its drastically dropped. Should I just remove the capacitor? I'm a newbie to electronics.

hii am a 3rd year btech ( electronics and communication )student.i have some basic idea abt the subject. could any one of u suggest some practical projects which i could do.It would help if the topic is a fresh and implementable one. i would like to do projects using a basic linear integrated ckt such as an op amp.

i have a project where i have 4 LED lights. i need each LED to come on or activate at its respected voltage. I.E, LED 1 comes on at 3v and 3v ony, LED 2 come on at 4V and 4v only ect........
i have thought about using AND gates, op-amp lm324, resistors, rely swichts, and ciruit brakers. the only thing with them ideas is that its going to make it that much harder, i know that its a easier way to do this, i feel it, i just need a lit help, what you think?? what can i build or buy that can tell the differents between what volts is being apply and only let though its set voltage. thanks a lot. every though is needed

PACE MBT 201A soldering station is an industrial type soldering equipment. my problem is that my soldering heater will overheat at settings "0" degress celcius for channels 1 and 2.....there is a circuit card inside it when i test all the OP-AMP ic its status is ok...check all the CAPACITORS AND RESISTORS all of them seems ok,which means there is no change in values.....can anyone help me determine what causes my soldering heater to overheat? thnxs!!!

hi friends,
I'm doing a project regarding the converting the TTL signal to NIM signal. However,the result from the simulation in MULTISIM do have a little diverse in real time simulation.
Here is my question,
1) i got the output square wave at the logic 0 recorded 600mv and logic 1 is -20mv. the result i wish to get is logic 0 record (range 1v to 0volt) and logic 1 is (-1.8v to -0.6v)...how to increase the gain of the level?by using operational amplifier? which type of op-amp i have to use?

thanks for helping hand

MY Circuit is: lamp , relay ,(IC:op-amp LM385) and push bottom and wanted to make lamp lights(ON) after i push the push bottom and after 5secnod the lamp off automatically the circuit simillar to the effect of the timer (IC 555 ) circuit
i install my project on breadboard (nonsoldered board) but it is not work
how can i troubleshooting the problem in this circuit?
help me by giving me methods of tests or wesites of troubleshooting or learn video to install it again from begin or a pdf book to install the circuit from the start step by step
please help me quickly i need the circuit work in agood condition
thaxn

In my laboratory experiment in Summing Amplifiers, I am given a summer amp with Rf = 150M-ohm, Ra = Rb = 150M-ohm, Va=2V and Vb=1V,

when i calculated the Vout by this equation:
Vout = -{ (Rf/Ra)*Va + (Rf/Rb)*Vb }
i got Vout = -3V
However when we try this in Multisim wherein we use 741 op-amp, Va and Vb are connected to pin 2, Vcc =12V at pin 7, Vee = -12V at pin 4, Vout at pin 6, and Rf (feedback Resistor) at pins 2 and 6; the value for Vout will be...
7.882V

Why is this so??? can someone help me on this...
I need help please...
thank you so much in advance! >_<;;;

Two ideas I have are:

1.)Using an Op Amp to convert the voltage into current with a Voltage Controlled Current Source circuit and then put the LED in the current source path.

2.)Identifying a small low power V-to-F or PWM circuit that simply converts the voltage into pulses where the brightness of the LED would then easily match the frequency or on-time rate.

Hello, as you may know that the output from the Pt100 sensor is in Ohms... I would like to amplify / convery the signal to 0-5 v using op-amp. Please let me know the proper circuit to do it.

I'm wondering if there are any electronic engineers about that that use Yahoo IM, AIM, or MSN, that wouldn't mind helping a VERY curious HS student out. I'm getting my 5th credit in electronics right now, so I know a quite a bit, but not as much as I would like to know.

Most of what I have been working on has been modifying electrical signals, such as audio signals, or sign waves that change frequency a little bit over time. Right now I am working with the 741 Op Amp, trying to convert a sine wave into a square wave, by use of comparator, having some problems with it.