Thanks for watching. For more Analog Circuit, Op Amp and Regulator Examples please see: Voltage Regulator Example: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rI9f6-DyXxQ.html Push-Pull Power Amplifier ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-866MYibo8yE.html Voltage Regulator Design with Darlington Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ArisQp7V0Ac.html Op Amp Analog Computer circuit that solves Differential Equation: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ENq39EesfPw.html Op Amp BJT JFET in Voltage Regulator design ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-CJl-urzeiTo.html Bandgap Video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-esMlNx5w9Jw.html PID Controller Circuit for Servo motor ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-NATBlfABXrA.html Sawtooth Oscillator with Op Amp, JFET and BJT Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5zHXTx-Vl20.html Full-Wave Rectifier: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-DJJMNU-CYcg.html And my analog playlist ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope these Analog Circuit Design and Analysis Examples are interesting and helpful. 🙏
Thank you for watching & your good question. Glad that you liked this voltage regulator circuit analysis video. For more example please see the Circuit Videos ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt . Regarding your question, Response time of the regulator (say to a sudden current surge due to for instance inadvertent shorting of output to ground) is mainly defined by the KPI (e.g. slew rate, max current, settling time, etc.) of the operational amplifier selected for this circuit. The low-current PNP and NPN BJT current limiting semi Szkilai pair transistors respond very fast as they just need the minimal turn-on voltage across the PN junction of emitter-base of PNP transistor. The cascade BJT pair (while in linear region) has a current amplification beta of at least 100. Hence a mere 50 micro amp emitter current of PNP BJT translates to 5 mA current steering from the output of Op Amp by the NPN BJT transistor. Note that in nominal operation, the Op Amp only needs to provide 1.2 mA to the base of the high-power Darlington transistor pair to support up to 1.2 A current at the output of this regulator. We can also adjust the value of the nominal 600 ohm resistor at the output of the Op Amp to optimize the response of the circuit. Both Analog Devices and Texas Instruments offer a number of good op amp choices that can be used for this voltage regulator design application (please see Analog Devices Op Amps www.analog.com/en/product-category/operational-amplifiers.html ). For more Analog Circuit, Op Amp examples please see: Voltage Regulator Example: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rI9f6-DyXxQ.html , Op Amp BJT JFET in Voltage Regulator design ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-CJl-urzeiTo.html Push-Pull Power Amplifier ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-866MYibo8yE.html Voltage Regulator Design with Darlington Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ArisQp7V0Ac.html Op Amp Analog Computer circuit that solves Differential Equation: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ENq39EesfPw.html And my Analog playlist ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope this explanation and additional videos are helpful in answering your question. 🙋♂ Thanks again
Thanks Dennis for watching and sharing your thoughts and feedback. I am thankful. There are many ways to wire components & transistors to build current limiting feedback (method shown here is not unique). With that said, please let me know why do you think the PNP-NPN transistor pair is not right? Notice that they are high beta transistors with low 10 micro amp to max ~10-20 mA current levels that are completely negligible compared with the output current levels. I will post more Voltage Regulator examples soon. In the meantime, please see more examples in the analog circuit collection ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope this explanation is helpful. Thanks again for watching. 🙏
Thanks for watching this voltage regulator circuit analysis example. I appreciate your feedback and follow-up questions. Please note that there are many ways to wire components & transistors to build current limiting feedback (method shown here is not unique). With that in mind, Notice that current limiting PNP-NPN transistors are high-beta transistors with low 10 micro amp to max ~10-20 mA current levels that are completely negligible compared with the output current levels. And regarding response time of the regulator (say to a sudden current surge due to for instance inadvertent shorting of output to ground) is mainly defined by the Op Amp KPI (e.g. slew rate, max current, settling time, etc.) of the operational amplifier selected for this circuit. The low-current PNP and NPN BJT current limiting transistors respond very fast as they just need the minimal turn-on voltage across the PN junction of emitter-base of PNP transistor. The cascade BJT pair (while in linear region) has a current amplification beta of at least 100. Hence a mere 50 micro amp emitter current of PNP BJT translates to 5 mA current steering from the output of Op Amp by the NPN BJT transistor. Note that in nominal operation, the Op Amp only needs to provide 1.2 mA to the base of the high-power Darlington transistor pair to support up to 1.2 A current at the output of this regulator. We can also adjust the value of the nominal 600 ohm resistor at the output of the Op Amp to optimize the response of the circuit. Both Analog Devices and Texas Instruments offer a number of good op amp choices that can be used for this voltage regulator design application (please see Analog Devices Op Amps www.analog.com/en/product-category/operational-amplifiers.html ). Please see more circuit examples in the analog circuit collection ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope these explanations and additional information are helpful. Thanks again for watching. 🙏
Nice explanation. But I see one mistake, or I consider it a mistake. RLmin is calculated and valid only for alpha=1. For lower alpha there will be different allowable RLmin (lower). And then the calculations for max power dissipation is wrong. If alpha=0, the Vo=6V, and RLmin=5ohms. Voltage drop on pass transistor is 13.4V, current 1.2A, and maximum power dissipation will be 16.08W
Thanks for watching and sharing your thoughts. I appreciate your detailed attention. One could even state that RLmin is zero because we already have foldback current limiter in this circuit that quickly protect the circuit. But, aside from the fact that I wanted to show how RLmin is calculated, it is not recommended to plan RLmin for different output voltages due to possible current spikes and surges beyond planned limits for transistors in this circuit in addition to requiring higher power BJT as you also noted. I will post more Voltage Regulator examples soon. In the meantime, please see more examples in the analog circuit collection ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope this explanation is helpful. Thanks again. 🙏
You're welcome. Thanks for watching & your encouraging comment. Glad that you liked this video. Please let me know the circuit topics that you are interested in seeing more in this channel 🙂. For more Analog Circuit, Op Amp examples please see: Voltage Regulator Example: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rI9f6-DyXxQ.html , Op Amp BJT JFET in Voltage Regulator design ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-CJl-urzeiTo.html Push-Pull Power Amplifier ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-866MYibo8yE.html Voltage Regulator Design with Darlington Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ArisQp7V0Ac.html Op Amp Analog Computer circuit that solves Differential Equation: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ENq39EesfPw.html And my Analog playlist ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt Thanks again 🙋♂
Nice as usual. Quick question here though, how can you say OP amp is operating with feedback when said feedback is done through OFF transistors .. ? Thanks
You're welcome. Thanks for watching & your good question. Negative Feedback for op amp is provided via voltage division across two 10k ohm resistors in series that feed the negative input terminal of the operational amplifier. For example, if output voltage suddenly increases then the voltage at negative terminal of op amp increases as well that results in op amp reducing its output voltage that then reduces voltage at base o Darlington transistor and hence results in reduction of output current and voltage (basically counteracting the initial voltage increase as expected from negative feedback). For more Op Amp & Analog Circuit examples please see: Op Amp Amplifier with Electronic Gain Control ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-NoNgQpbj77Y.html Analog Logarithm Computer ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RpKEq5WyoLg.html Op Amp Analog Computer Differential Equation Solver ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ENq39EesfPw.html Thermometer Circuit Design with Op Amp & BJT transistor ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-55YsraFE0rg.html Push-Pull Power Amplifier with Darlington Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-866MYibo8yE.html Sawtooth Waveform Generator design with OpAmp, JFET, BJT ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5zHXTx-Vl20.html Wilson Current Mirror and Current Source Design ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LfbfJYrovN0.html Instrumentation Amplifier with Electronic Gain Control ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-C4tghZ-q6Zs.html Programmable Current Source Design with Op Amp, Zener Diode and Digital Potentiometer ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-R1x6B0TczWk.html I hope these videos are interesting as well. 🙋♂️
I need to analyse circuits like you Prof. My problem is knowing where to start on a given cct, at the moment I couldn't get very far on my own, but am learning fast thanks to your videos.
Thanks George for watching and your encouraging comment. Glad to hear that you are making good progress and my videos are helpful.🙏 For more Circuit and Op Amp Examples please see my Circuit Videos playlist ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope these Analog Circuit Design and Analysis Examples are interesting and helpful. 🙏
Thanks for watching and your follow-up question. I appreciate your interest. I don't mean to indicate units should be written as superscript. It is just mostly matter of lack of space (in front of the number) and/or a way to highlight the unit and scale (e.g. mV, uA, etc.). For more Circuit examples please see ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope this explanation is helpful. 🙋♂️
You're welcome. Thanks for watching and your question. There are different methods for designing voltage regulators that depend on target design requirements and Key Performance Indicators (KPI). For more regulator examples please see: Voltage Regulator Design with BJT Darlington Transistors and Zener Diodes ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ArisQp7V0Ac.html Voltage Regulator Design with Op Amp ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rI9f6-DyXxQ.html Voltage Regulator design with Op Amp BJT JFET ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-CJl-urzeiTo.html I will post more voltage regulator circuit design examples soon. I hope this is helpful. 🙏
You are welcome. For more Electronic circuits examples please see ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope these Analog Circuit Examples are helpful.
Wouldnt the max power of the Darlington pair be when alpha = 0?, this would mean output voltage is 6V, and the voltage drop across r would be 0.6 V then VCE would be 20V - (6V + 0.6V) = 13.4V and power would be 13.4V * 1.2A = 16.08W, all of this while staying within expected ranges
@@josemanuelromo6832 thanks for your good question. This problem states that the minimum load resistor allowed is 10 Ohm. Hence the max output current is 1.2 Ampere that ONLY happens when output voltage of regulator is 12 Volts (meaning alpha is one). When alpha is set to zero, then output voltage is 6 Volts which results in max output current of 600 mA when minimum allowed load resistor of 10 Ohm is applied. I recommend that you also watch minute 21:10 onward that further explains by showing and plotting the Transistor Power Formula. I hope this is helpful.
Neat video and circuit analysis! If I may add: I would replace the Zener Diode with a TL431 or any other reference to get more stability on the output voltage throughout the temperature range!
Thanks Matthias for watching and sharing your thoughts and suggestions. Glad that you liked this regulator circuit analysis video. Your TL431 Shunt Voltage Regulator from Texas Instruments is a good alternative solution with more temperature stability instead of Zener Diode 1N5233 (from Vishay Semiconductor) if its 0.038% temperature coefficient (70mV change in 6V reference per 30 deg C junction temp change) is not low enough for a given application. For more examples please see ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope these Examples are interesting and helpful. Thanks again 🙏
Thanks for watching and your thoughtful comment. I just checked again and could not observe any major issue. Please refresh your page and watch again possibly in Firefox browser and if you still observe any issue then please let me know at what moment or minute you observe it happening. For more Analog Circuit, Op Amp examples please see: Voltage Regulator Example ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rI9f6-DyXxQ.html , Op Amp BJT JFET in Voltage Regulator design ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-CJl-urzeiTo.html Push-Pull Power Amplifier ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-866MYibo8yE.html Voltage Regulator Design with Darlington Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ArisQp7V0Ac.html Op Amp Analog Computer circuit that solves Differential Equation: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ENq39EesfPw.html And my Analog playlist ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt Thanks again 🙋♂
If I'm not mistaken, this one will have issues sinking currents (e.g. variable reactive loads) . Assuming an overvoltage injected in/by the output, the PNP is blocked (its base is at higher voltage than its emitter) and the overvoltage can only try to drive the current through the darlington in reverse.
Thanks for watching and sharing your thoughts and feedback. It is helpful and encouraging to hear back and further learn. This regulated DC voltage supply is mainly designed for resistive load. Using and analyzing it for a reactive load require further evaluation, modification and potentially additional restrictions. I will try to post videos about more flexible Voltage Regulators. In the meantime, please see more circuit examples in the analog circuit collection ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope this is helpfull. Thanks again for watching. 🙏
@@STEMprof Thank you. "I will try to post videos about more flexible Voltage Regulators." I'm waiting for them, then. In re: "is mainly designed for resistive load" - wouldn't hurt to mention this in the video comments.
Thanks again for watching and your good suggestions and feedback. I am thankful. Sure, will post more videos soon and will try to mention details as much as I can. 🙋♂️
I tried and tried to respond directly to your comment below, bur for some reason the system was completely ignoring me when I hit the reply button, so I am doing it this way. . I must have misread your schematic, thinking you were using all NPN transistors. I can see how your PNP/NPN combination would work for current limiting. I apologize for my error. I thought I had checked the transistor type multiple times before making my comment....... . If you HAD used an NPN for the current sense instead of a PNP you could have performed the same function with one less transistor. Your series pass Darlington configuration needs a resistor from base to emitter to minimize or eliminate the effects of leakage on the second transistor in the pair, and your current limiter might ground the base of the first transistor, but would not be able to eliminate the leakage current in the second transistor. And since it will be the one generating all the heat, the leakage really has to be considered. If you use an off-the-shelf darlington power transistor instead of creating your own, you will not have to worry about leakage because the off-the-shelf parts have those resistors already in the part. . I will be looking for those future videos you mentioned. Thank you.
Thanks again Dennis for watching and for sharing your thoughts and feedback. I appreciate your follow-up comment. Glad that the issue is resolved. Thanks also for sharing your practical advice regarding base-emitter resistor to counter leakage. I will post more examples and I hope that you find them interesting as well. In the meantime, please see more circuit examples: Voltage Regulator Example: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rI9f6-DyXxQ.html Voltage Regulator Design with Darlington Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ArisQp7V0Ac.html And the Analog / Op Amp circuits videos playlist ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt I hope you enjoy the circuit videos 🙋♂️
I also think the current foldback function could be implemented with only NPN transistor, but in that case the current sense resistor would have to be installed on the negative side of the supply and that would affect the voltage control (the voltage applied to load would not be the same as intended. One correction would be to change the voltage reference accordingly and take the zener anode from the current sense resistor
@@anoimo9013 Thanks for watching & sharing your thoughts. Glad that this video is bringing these good comments. To your point there are many ways to design a target voltage regulator. For more examples pls see: Voltage Regulator Example: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rI9f6-DyXxQ.html , Op Amp BJT JFET in Voltage Regulator design ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-CJl-urzeiTo.html Voltage Regulator Design with Darlington Transistors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ArisQp7V0Ac.html Push-Pull Power Amplifier ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-866MYibo8yE.html And my Analog playlist ru-vid.com/group/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt Thanks again 🙋♂
