Episode 1132 I show two ways to apply an offset voltage to a circuit. I change a 0 to 2 volt signal into a +4.7 -4.7 volt signal Be a Patron: / imsaiguy
I’m very new to electronics and have been learning about op amps. I’m designing a circuit where I need to scale a control voltage of 0-5v to -4v to 4v. I’ve scoured the web trying to figure it all out and finally came across this video. You have explained it so clearly, I now know exactly what I need to do. Thank you so much!
You can think of the transfer equation as a liner function (a line) and use the point slope formula: Y=mX+b,where m is the slope of the line: m = (Y2-Y1) / (X2-X1). and design the op amp circuit to output: "when X=0, Y= -4, AND when X=5, Y=+4). --dALe
Great explanation! I remember op amp circuit design being my favorite in college. Back then they seemed to operate by magic. Now after a couple of decades in the field, experience has taken some of that 'magic' away, but they're still my favorite thing to play with even today 😁
Usefull video, thanks. Op amps are really amazing, but tricky:) All this feedbacks, different circuits you can make with them. It takes time to understand them and much more time to learn how to calculate them)
If you go through the mathematics, you find that NEITHER of these circuit configurations allows gain AND offset to be independent! For this you need TWO op amps.... 1) first amp is connected as an inverting amplifier with FIXED input and feedback resistors with the variable offset voltage (Voff) applied to the non-inverting input. You get an offset of 2Voff (I may have to have to check this) at the output. 2) Then you feed this op amp's output into a standard inverting amp and adjust the gain resistor (Rf). 3) The two op amps MUST be connected with the offset amp feeding the gain amp. Also, this gives an output that is not inverted!
In the second circuit, the input has Voff reference while the output is still ground referenced; this is why the offset is not 1 V. If the inversion is not desired, you can always use a difference amplifier, apply the signal to the + chain, and +1 V to the - chain.
Great video! Thanks for uploading. I'm currently troubleshooting an op-amp which has a constant bias input of 2.56V at the (+) input pin, and NO SIGNAL on the (-) input pin, yet I am still getting 2.56V at the output of the op-amp. The op-amp supply rail is +8V and -8V and tested out to be just fine with or without the op-amp in circuit so I have eliminated the supply voltage circuit as an issue. In your experience with faulty op-amps, have you ever run into this scenario?
Great info, thank you sir. Has me thinking about and thinking I'll need to review again for potential cost effective designs for DIY DCEP & DCEN offset adjustments for an AC (I think is pulsed DC technically albeit with potential range of waveforms?) welding aluminum option on an older machine that doesn't have the nicer frequency and offset controls. I still haven't gotten to reviewing the schematics of the original Miller Synchrowave design(s), since when I get around to again I wanted to start from basic theories/apps. Very inspirational thought provoking where I'm guessing will be done using transistors for higher current applications since I don't recall ever seeing a higher current capable op-amp.... where like transistors one could arrange in parallel even to deal with the current needs.
GREAT VIDEO!!!! I did as you suggested and "built it myself". Incoming question....instead of the 47k resistor, I used a 100k pot in order to adjust the gain, along with the variable offset, as you did, on the "+" input. My goal was to make an op amp with INDEPENDENT gain and offset. When I adjusted the gain, I think the offset was changing as well. Soooo, with this circuit, is the offset supposed to alter (at all) when the gain resistor is adjusted????? Or should they be 100% mutually independent. I did have sort of a 'rat's nest' breadboard with no filter caps. YOUR REPLY WILL BE GREATLY APPRECIATED AS I AM IN GREAT NEED OF SUCH A CIRCUIT!!!
In the inverting op amp example you have the + input grounded. In some circuits this + input is grounded through a resistor. What is the purpose of this resistor? My circuit example is used as a meter scaling circuit, where a voltage drop across a resistor is amplified to drive an analog meter.
Thanks! I know that your example was for a motor. However, if you wanted to use this circuit with audio, what are the considerations of having added DC offset? In other words, I know that DC offset is bad for speakers... So, what is needed to prevent that damage, if this circuit is employed?
yes you would not want dc offset on a speaker. but if you are designing an audio amp that runs off a 9v battery then you will need to offset the signals by 4.5v to be in the center of the opamp. the very last output to the speaker would have a large capacitor to remove the dc.
@@IMSAIGuy "the very last output to the speaker would have a large capacitor to remove the dc." I knew of a cap being the last item in the chain to remove the DC, but, I thought it was a precaution to remove unintentional DC. I had not thought of adding DC intentionally and then adding a cap to quench its negative effects. Hmm... I need to give it a bit of thought and experimentation. Thanks for the reply.
Hello, i would like to ask you if is it possible to realize a simple circuit that i have in mind. I have an arduino that can menage Voltages between 0 and 5 V. I just bought a little ADC module that can performe 12 bit conversion to get signals like LFO for musical purpose. What i need here is to tranform voltages that goes from 0 to 5Volts to something like -10 to + 10Volts. I have a dual power suplly -12 to +12Volts. If i understood i need to build that circuit with an amplification gain of something like 4. Hope you can help me Thanks
so I have this background obsession with dc (stepper) motors, where i noticed as a kid that if you connect the windings, and turn one, the other will turn because of the energy generated by the other. But obviously it's not much power and the motors will slip and miss steps. I've always thought that it should be possible to add power to the circuit with op-amps and comparators, to "stiffen" the response... but I don't quite know how to do it. Is this something you would be interested in explaining/investigating?
@@nickcaruso I haven't played with the stepper motors much yet... though you have me thinking about how some operate old metal lathes and 3-phase machines on two phases (240VAC) into a 3-phase driver motor larger enough than the driven 3-phase motor and a 1-phase motor to get the 3-phase driver motor spinning enough to meet performance requirements. Probably not a need for stepper motors... though maybe and the old fashion inverting/converting methods came to mind (like DC to AC and AC to DC using motor & alternator/generator) and is somewhat on topic... though not quite. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-e6eKDsDpup8.html
