Found your excellent books a few years back and stumbled upon you youtube videos recently and all I want to say is thank you for this gift that helped me through my university years and keeps helping me to this day. Clear ,concise and of high quality.
Edit: I saw your intro video, circuit simulator is TINA-TI. Would be nice to have in each video description. Great content, I don't know why you aren't 10x bigger!
Hello! I'm interested in learning about op-amp compressors. I would greatly appreciate it if you could create a tutorial that teaches the basics of how op-amp compressors work, what components are needed to build one, and the typical circuit configurations. An overview of the theory behind compression and why certain design choices result in different compression characteristics would also be very helpful context. Please let me know if a tutorial on this topic is something you are able to provide. Either way, thanks for your time and consideration!
Check out Moritz Klein. He has a circuit that I am experimenting with. Only problem is that it is designed to work at Euro Rack level (aprox 5V I think) rather than line or instrument levels. I am trying to modify it to fix this problem (for my use).
Usually this is done by having an electronically controlled resistive device in the feedback loop of the op amp to control the gain. One example is having the input signal applied to a light which is then encapsulated with an LDR (light dependent resistor). As the signal increases, the light increases, and that makes the resistance drop. Another possibility is using a JFET in the ohmic region instead of the LDR. A third option (a bit fancier) is to use an OTA (operational transconductance amplifier) to create a VCR. I designed a system using an OTA in the pre-MIDI days to create a touch-sensitive electronic drum system. I'll see if I can come up with something for a video (not immediately though, as I have other irons in the fire).
Hello Professor, I do like your videos as they are short and to the point. I am thinking of running some of these circuit for learning purposes. The signal level in your circuits is much higher than the levels that my sig gens produce. It looks like I could cut the values down by a factor of 4 or 5 (including the diodes) or put an op amp amplifier in front? Did you do a vid on the audio limited (controlled gain)?
I haven't done anything specifically on an audio limiter but there are some related videos in the op amps playlist. Also, see my reply to Black_Engineer in this comment section.
This is what I would call a "soft" clipping circuit, evidenced by the rounded corners as the circuit goes in and out of clipping. An interesting variation on this circuit is what I would call a "hard" clipping circuit, where the output is faithfully produced right up to the clipping point and then clamps at that point. This can be done with the addituon of one resistor and repositioning the clamping diodes. I leave it as an exercise for your students to implement a version of this circuit. 🙂🙂
I am wondering, is there a reason you put the diodes in the Feedback path, rather than parallel to R_Load ? Im asking because it looks to me very much like a Bidirectional TVS diode an in my opinion putting the diode parallel to the Load conveys the function of it better.
Placing the diodes across the load would effectively short out the op-amps output once they start to conduct. Not only is this bad for the op-amp, it's bad for the diodes and it also affects the output impedance which may not play nice with the input impedance of the following stages.
@@JaenEngineering Pretty much! If you do a sim with an ammeter at the op amp's output (prior to the feedback node), you can see that the current waveform is fairly well controlled. If you then move the Zeners in parallel with the load and rerun the sim, you will see that the current waveform will be highly distorted and at a much higher level. Placing the diodes in the feedback loop allows the load to be somewhat isolated from the diodes and also controls both the input impedance and output impedance, along with the possibility of voltage gain. Now imagine what the signal source would see if you just had the diodes in parallel with the load. That could be highly non-linear load impedance, and who knows how the signal source would react!
This circuit is not a "precision" clipper. It is a sloppy soft clipper. It's soft because of the knees of the zeners, and it's sloppy because you never know what a zener's actual voltage will be. If you want a precision clipper, you send a reference voltage through a resistor to the inverting input of the opamp, put a diode at the output of the opamp, connect the other end of the diode to the inverting input and take the clipped output from there. You can change the direction of the diode to clip to a negative voltage. This circuit has two issues, though: The first is that, if you want both positive and negative clipping, you must put two opamps in series. The second is that the output impedance will be whatever the resistor value is, so you need to follow this circuit with a buffer, which uses another opamp.
This is referred to as "precision" because it's higher quality than just using standard passive resistor-diode circuits (limited by the op amp's speed, of course). It is easily programmed by setting the Zener potentials. One of the primary benefits of this circuit is its simplicity: an op amp, a couple of resistors and diodes, and you're good to go. Thus, it is a good, general purpose signal limiter. If you need something that is more precise, by all means, make something more complicated that fits your needs.
@@ElectronicswithProfessorFiore Well, it seems to me that if you want precision, that implies an exact voltage. For example, say you want to limit the output of a comparator to exactly 5V and 0V for use in a subsequent integrator. For that, 5.1V back-to-back zoners would be a disaster, but a trimmed LM336V5 into a 10k resistor and a 1N4148 diode do the job perfectly. I build and sell enough electronic devices (synthesizer modules) to know when precision truly matters.
@@docsketchy Well if you want to argue a "precise" definition for "precision", be my guest. FYI, before my many years as a college professor, I worked in an instrumentation calibration lab for a very large company, so yeah, I have an idea of what precision means as well. Like all of engineering, it comes down to how much you need for a specific application, and balancing that against other factors such as cost. In any case, you might be interested in this related video (which can be configured as a limiter, details in my free textbook-see links in description): ua-cam.com/video/lUST4lCa9UU/v-deo.html
Found your excellent books a few years back and stumbled upon you youtube videos recently and all I want to say is thank you for this gift that helped me through my university years and keeps helping me to this day. Clear ,concise and of high quality.
Glad you found it useful. Tell your friends ;-)
@@ElectronicswithProfessorFiore I most certainly will!
Edit: I saw your intro video, circuit simulator is TINA-TI. Would be nice to have in each video description. Great content, I don't know why you aren't 10x bigger!
Hello! I'm interested in learning about op-amp compressors. I would greatly appreciate it if you could create a tutorial that teaches the basics of how op-amp compressors work, what components are needed to build one, and the typical circuit configurations. An overview of the theory behind compression and why certain design choices result in different compression characteristics would also be very helpful context. Please let me know if a tutorial on this topic is something you are able to provide. Either way, thanks for your time and consideration!
Check out Moritz Klein. He has a circuit that I am experimenting with. Only problem is that it is designed to work at Euro Rack level (aprox 5V I think) rather than line or instrument levels. I am trying to modify it to fix this problem (for my use).
Usually this is done by having an electronically controlled resistive device in the feedback loop of the op amp to control the gain. One example is having the input signal applied to a light which is then encapsulated with an LDR (light dependent resistor). As the signal increases, the light increases, and that makes the resistance drop. Another possibility is using a JFET in the ohmic region instead of the LDR. A third option (a bit fancier) is to use an OTA (operational transconductance amplifier) to create a VCR. I designed a system using an OTA in the pre-MIDI days to create a touch-sensitive electronic drum system. I'll see if I can come up with something for a video (not immediately though, as I have other irons in the fire).
@@ElectronicswithProfessorFioreThank you!
@@jimbelcher6877Thank you too!
Hello Professor, I do like your videos as they are short and to the point. I am thinking of running some of these circuit for learning purposes. The signal level in your circuits is much higher than the levels that my sig gens produce. It looks like I could cut the values down by a factor of 4 or 5 (including the diodes) or put an op amp amplifier in front? Did you do a vid on the audio limited (controlled gain)?
I haven't done anything specifically on an audio limiter but there are some related videos in the op amps playlist. Also, see my reply to Black_Engineer in this comment section.
This is what I would call a "soft" clipping circuit, evidenced by the rounded corners as the circuit goes in and out of clipping. An interesting variation on this circuit is what I would call a "hard" clipping circuit, where the output is faithfully produced right up to the clipping point and then clamps at that point. This can be done with the addituon of one resistor and repositioning the clamping diodes. I leave it as an exercise for your students to implement a version of this circuit. 🙂🙂
I am wondering, is there a reason you put the diodes in the Feedback path, rather than parallel to R_Load ? Im asking because it looks to me very much like a Bidirectional TVS diode an in my opinion putting the diode parallel to the Load conveys the function of it better.
Placing the diodes across the load would effectively short out the op-amps output once they start to conduct. Not only is this bad for the op-amp, it's bad for the diodes and it also affects the output impedance which may not play nice with the input impedance of the following stages.
@@JaenEngineering Pretty much! If you do a sim with an ammeter at the op amp's output (prior to the feedback node), you can see that the current waveform is fairly well controlled. If you then move the Zeners in parallel with the load and rerun the sim, you will see that the current waveform will be highly distorted and at a much higher level.
Placing the diodes in the feedback loop allows the load to be somewhat isolated from the diodes and also controls both the input impedance and output impedance, along with the possibility of voltage gain. Now imagine what the signal source would see if you just had the diodes in parallel with the load. That could be highly non-linear load impedance, and who knows how the signal source would react!
This circuit is not a "precision" clipper. It is a sloppy soft clipper. It's soft because of the knees of the zeners, and it's sloppy because you never know what a zener's actual voltage will be. If you want a precision clipper, you send a reference voltage through a resistor to the inverting input of the opamp, put a diode at the output of the opamp, connect the other end of the diode to the inverting input and take the clipped output from there. You can change the direction of the diode to clip to a negative voltage. This circuit has two issues, though: The first is that, if you want both positive and negative clipping, you must put two opamps in series. The second is that the output impedance will be whatever the resistor value is, so you need to follow this circuit with a buffer, which uses another opamp.
This is referred to as "precision" because it's higher quality than just using standard passive resistor-diode circuits (limited by the op amp's speed, of course). It is easily programmed by setting the Zener potentials. One of the primary benefits of this circuit is its simplicity: an op amp, a couple of resistors and diodes, and you're good to go. Thus, it is a good, general purpose signal limiter. If you need something that is more precise, by all means, make something more complicated that fits your needs.
@@ElectronicswithProfessorFiore Well, it seems to me that if you want precision, that implies an exact voltage. For example, say you want to limit the output of a comparator to exactly 5V and 0V for use in a subsequent integrator. For that, 5.1V back-to-back zoners would be a disaster, but a trimmed LM336V5 into a 10k resistor and a 1N4148 diode do the job perfectly. I build and sell enough electronic devices (synthesizer modules) to know when precision truly matters.
@@docsketchy Well if you want to argue a "precise" definition for "precision", be my guest. FYI, before my many years as a college professor, I worked in an instrumentation calibration lab for a very large company, so yeah, I have an idea of what precision means as well. Like all of engineering, it comes down to how much you need for a specific application, and balancing that against other factors such as cost.
In any case, you might be interested in this related video (which can be configured as a limiter, details in my free textbook-see links in description): ua-cam.com/video/lUST4lCa9UU/v-deo.html