Amp 50-150mV

Usually a capacitor is used to add voltage to bias the transistor while letting the signal through.

http://everycircuit.com/circuit/6222721632698368

Why, because it acts as a buffer from the voltage divider that keeps the transistor at its Q-point without loading down on the signal?

But how can you use a capacitor for amplifying dc signals, for say small linear changes in the signal, in which a capacitor would not work as well in that situation, right?

Why would you want to amplify a DC signal? Is this not for audio? If so, you should say, because when somebody sees “amplifier” without anything else saying what type of amplifier, they think audio amplifier.

Because not all amplifiers are strictly designed for ac, there are pleanty of applications in dc as well.... like in my case for example: Amplifying the extremely small voltage drop produced across a shunt resistor for sensing the amount of current flowing through a load

I see. But i can’t help but notice the ever present 3-4mA the circuit pushes into the input. For this kind of application your mentioning, the average person would just use a high gain differential amp, a.k.a. an op-amp, to amplify the signal. It’s too much trouble just to design your own amp when you have a bunch of cheap op-amps laying around that would actually perform better than most things you could design.

@Jason9 a lot of instrumentation sacrifice 4mA for exactly that purpose, that is why they run 4 - 20 mA signal loops.

Thanks, I understand what your saying, but I'm always trying to design it myself because I don't have an op amp and I've never used one, I might be able to salvage one from something else... but then again, aren't there a bunch of different op amps out there, I have no idea which is which, when to use this one, or whichever version of op amp would suit me the most. Honestly, I've just been avoiding buying one for a while just cause I've never really used one

And to tell you the truth, I've hardly ever even used one in any of my simulations

First, practice with them in the simulation. Their really quite simple once you realize how they work and how they behave to negative feedback. If your using them as an amplifier, then you can send a signal to the positive input and then take a resistor voltage divider and attach one end to the output of the op-amp, attach the middle to the negative input, and attach the other end to your reference voltage (usually either ground or half-way between your two supply voltages (the positive one and ground assuming your not using a negative supply). You can practice in the simulation with using a potentiometer as the negative feedback. Because of the high gain, the op-amp will put whatever voltage on the output that is required to make sure the inputs are both at the same voltage. If you’re going to buy one, and if you’re using it for a high frequency application then look for something with a high slew rate and rated for the frequencies your using it at, or higher, and no matter the application, make sure the op-amp is rated to output as much current is required by the application, and if there are none that will give enough current, add a current amplifying stage to the end (like two transistors, one NPN and the other PNP, with their emitters facing into each other, and biased by two diodes and the output of the op-amp at the junction between the two diodes). By the way, I’m just curious, how old are you?

Ok I'll try all that, thanks. I just turned 19 about a month ago

Are you in college? Or did you quit school after high school?

I'm not in college yet, but I do have plans to go so I can get a bachelor's or master's degree in electronics engineering (on the semiconductor level). I'm just not sure how I'm gonna get there, whether I'm gonna work through it, or do it through the military in the Airforce, Navy, or Coast Guard, whatever I can do to avoid getting in debt with student loans. I've got a lot to think about. And I'm part of a big family while working a full time job, so it's hard to find time to do anything or think to myself. With siblings between several ages... a newborn, 2-year old, 5-year old, 11-year old, and a 16 year old at home. If I had a lot more time to, I'd be studying electronics more too. I can hardly even get the time to use this app.

But I've been really trying hard to get the time to do some other things, like surfing before I go into work... which is very fun by the way, do try it and it will stick with you for the rest of your life, it's really amazing to feel the waves pick you up and drive you forward with nothing but a board with fins and the power of the ocean! 🌴🌊🏄‍♂️😉

Too bad your so busy. Surfing does sound fun though.

Yeah I know, it sure is haha... you should go out and try it sometime!

@Issacsutt, try to balance all things in life is the most difficult thing. Not to much surfing or electronics or familie. Everthing in a weighted dosis 😁

Haha, ok. I'll keep that in mind, Thanks Hurz

Its my personal experience 😉

:)