newbie question about op amps - Page 1
Forum section: electronics / beginners

author: RivaultUser
author_rank: Contributor
timestamp: March 11, 2013, 01:31:45 am
content: what is the different between non inverting and inverting inputAll that i know is non inverting is the plus signal input and inverting is the negative signal inputBut what does it mean by inverting and non inverting itself???Also, I've seen a few of the configuration of op amps and I've found that there are non inverting amplifier and inverting amplifier. DUDE, I'M M REALLY CONFUSED ABOUT ALL OF THIS INVERTING THING. THEY ARE EVERYWHERE !!?!?!?!?!?!?Please helpppppp................Note :My friend ask me is it okay if he reverse the plus and negative signal of the audio input ?He's making an amplifier for his cellphone to the speaker

author: Rerouter
author_rank: Super Contributor
timestamp: March 11, 2013, 01:38:42 am
content: its just the way op amps work, any variation in the inverting terminal will result in the opposite at the output, so if you lower the - input you will see the output increase, while for the non-inverting, if you see the + decrease the output will also decrease,in truth all an op amp does is amplify the difference between + and - but depending on how you set them up you can bias a direct or inverted amplification,

author: ignator
author_rank: Regular Contributor
timestamp: March 11, 2013, 01:51:20 am
content: Quote from: RivaultUser on March 11, 2013, 01:31:45 amI hope your not starting on something way beyond your skill level.please readhttp://en.wikipedia.org/wiki/Operational_amplifierIt's possible to hack a circuit without any electronic knowledge other then "understanding door bell circuits". But you will just be making blind connections without understanding how opamps work.Theidealopamp has infinite gain, zero output impedance (resistance), infinite input impedance. This is needed to develop the formulas for an inverting amplifier, and non inverting amplifier. In either configuration, feed back must be provided from the output through a resistor network to the inverting input. The network can be zero ohm (and infinite) resistors in the case of a non inverting gain of 1 amplifier. The intent of using a differential amplifier is to reject common mode noise. Where typically you connect the ground reference of your signal source, and your signal source in a differential mode connection. The noise that is common is rejected, and not amplified. This is the typical usage of these amplifiers. They also can have inductors and capacitors added to make low pass, high pass, band pass filters.In the case of the inverting input, it takes the signal and inverts it, and passes it to the output. The amplifier takes what ever differential voltage at inverting/non inverting, and amplifies it by infinity (see actual specification for a real device which has finite gain but it's very large millions and more). Also look up differential amplifier, as this will give you insite if you have enough back ground knowledge.

author: BravoV
author_rank: Super Contributor
timestamp: March 11, 2013, 01:55:20 am
content: Suggesting to spend some quality time here 1st ->http://openbookproject.net/electricCircuits/Semi/SEMI_8.htmlThat question is way too basic, its like asking whats the difference between delete and backspace buttons.

author: IanB
author_rank: Super Contributor
timestamp: March 11, 2013, 02:01:42 am
content: Quote from: RivaultUser on March 11, 2013, 01:31:45 amExactly. That is the question an op amp asks: "What is the difference between my non-inverting and inverting input?"QuoteUnfortunately that is not right. Both inputs are plus signal inputs.QuoteTo invert something in electronics means to turn it upside down, to make it the opposite of what it was. So if you had a +2 V signal and you inverted it you would have a -2 V signal. (Be careful, though, because this is not what inverting means in mathematics.)So, take your op amp. Apply a +3 V signal to the (+) non-inverting input, and apply a +2 V signal to the (-) inverting input. The op amp inverts the +2 V signal to get -2 V and then it adds the two signals together. So (+3 V) + (-2 V) = (+1 V). The op amp sees +1 V and amplifies this.

author: RivaultUser
author_rank: Contributor
timestamp: March 11, 2013, 02:17:35 am
content: Quote from: BravoV on March 11, 2013, 01:55:20 amWell, after read i read that. It seems that i just ask why sun is called sun :-)Thanks for sharing your reference :-)

author: RivaultUser
author_rank: Contributor
timestamp: March 11, 2013, 02:19:33 am
content: Quote from: ignator on March 11, 2013, 01:51:20 amWell, sometimes i need to push myself beyond my limit &in the process of doing that I encountered stupid questionsThanks for your help man :-)

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: March 11, 2013, 02:20:10 am
content: Why am I so soft in the middle when the rest of my life is so hard?

author: Dongulus
author_rank: Regular Contributor
timestamp: March 11, 2013, 10:44:40 am
content: It's best for a beginner to think of an Op Amp as an amplifier that amplifies the difference between the + and - inputs with extremely high gain. For example, a voltage of 1.0001 V at the + input and 1 V at the - input will cause Vout to blow up to the power supply rail, say +15 V. Likewise, if the voltage at the - input is larger then Vout will drop to -15 V.Now, an Op amp doesn't seem like a useful device if all it does is crash over the smallest voltage differences. But, this only happens in "open loop" configurations. When feedback is introduced between Vout and Vin, more useful circuits are born. Both the inverting and non-inverting amplifiers use negative feedback where any difference between the + and - inputs causes the opposite change in Vout (hence NEGATIVE). Effectively, a feedback circuit allows Vout to influence the voltage at the Vin node ( the + terminal for a non-invert amp and the - terminal for the invert amp) which virtually eliminates the input voltage difference (i.e. V+ = V-). This assumption that V+ = V- is crucial for understanding any op amp circuits that you will encounter.I hope this clarifies some of the information that you have received.