Don't ad-block us - support your favorite websites. We have safe, unobstrusive, robotics related ads that you actually want to see - see here for more.
0 Members and 1 Guest are viewing this topic.
Have you tried using a 470ohm and 100ohm instead?An ideal op amp has infinite input impedance, real op amps don't. The resistances you are using could be getting close to the input impedances of the op amp.
I am using an LM358 op amp with +/- 5v power supply. I am inputting a signal that ranges from .25-.5v and I am trying to amplify it 4.7x using a 470k ohm and a 100k ohm resistor.
The only thing the op amp output does is give me a slightly diminished version of my input signal, say .28-.47v. I should also note that inputting a larger signal say 2v-2.25v seems to correct the problem.
Does anyone know what is going wrong? I have also ran simulations in Pspice and everything works perfectly. I would think the op amp could handle an input signal in this range. I am pretty sure it is connected properly. I am using this configuration http://en.wikipedia.org/wiki/File:Op-Amp_Non-Inverting_Amplifier.svg with r2=470k and r1=100k for the non-inverting amp.
now that i think of it, could it be the Vin that is causing the problem? It has no problem amplifying a 1.5v battery and when i bias my Vin with the 1.5v it will amplify the 1.5v but it won't amplify the swing of the voltage... i.e. say i multiply the voltage by 2, then the battery gets amplified up to 3v but my Vin only has a .25v swing as it did without the bias.
Are you using a solderless breadboard?-- Yes
Did you passivate the unused op-amp in the packet (or is it oscillating the heck out of both)?-- i don't understand what this means.
Did you 'scope the output or did you just use a voltmeter?-- voltmeter
From what source does the 0.25V to 0.5V come?-- it comes from a radio controller receiver.
[...] would i be able to integrate the signal with an op amp integrator circuit?
well I would like to be able to read the value into a micro controller, and then have the micro controller run an esc with its pwm output.
I am using an Arduino ATmega1280 if you are familiar.
Maybe you can point me in the right direction I was think about using PulseIn() but that sounds really inefficient