Temperature-Compensated Programmable Current Source Circuit Design with Zener Diode, BJT Transistors
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- Опубліковано 24 сер 2024
- How does a temperature-compensated adjustable current source work and how is it designed are the questions that are discussed in this electronic circuit design video. This programmable current source is designed using Zener Diode, Digital Potentiometer and matched BJT transistors. The formula for the output current of the circuit is computed as a function of circuit components. The potential choices of circuit components are also discussed including the 1N5228 Zener Diode from Vishay semiconductor with a negative temperature coefficient, the matched PNP Bipolar Junction Transistor pair BCM857 or PMP5201 from Nexperia,, and the AD8400 or AD5232 256-position Digital Potentiometer from Analog Devices.
For more analog circuit examples see:
Wilson Current Mirror and Current Source Design ua-cam.com/video/LfbfJYrovN0/v-deo.html
Temperature-Independent Current Circuit Design with Op Amp, BJT, Zener, Schottky Diodes ua-cam.com/video/hFbnjbddUvs/v-deo.html
Thermometer Circuit Design with Op Amp & BJT transistor ua-cam.com/video/55YsraFE0rg/v-deo.html
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Programmable Current Source Design with Op Amp, Zener Diode and Digital Potentiometer ua-cam.com/video/R1x6B0TczWk/v-deo.html
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For more analog circuits and signal processing examples see: ua-cam.com/play/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt.html
I hope these Circuit design and analysis videos are helpful.
Thank you for sharing.
You are welcome. Thank you. For Temperature Independent design please see alternative technique in ua-cam.com/video/hFbnjbddUvs/v-deo.html which is a current generator circuit design using Zener Diodes, Op Amp and matched BJT Transistors.
Thanks for that, very interesting circuit. I don't have access, at the moment, to my components or bench so I am wondering how it would perform in real life if I assembled the circuit exactly the way it was calculated.
You are welcome! Thanks for your interest in this circuit.
BJT beta increases with temperature, so the voltage across Rp varies with temperature.
Rp should be a PTC thermistor that tracks the beta.
Did clearly didn't even bother watching the video? 🙄
Thanks for watching and sharing your thoughts. You have a good point. If changes in beta of the main PNP transistor is not negligible then I suggest using alternative design in ua-cam.com/video/hFbnjbddUvs/v-deo.html which is a Temperature-Independent design using Zener Diodes, Op Amp and matched BJT Transistors. If need be a current inverter can also be used to change current sink to current source circuit. Thanks 🙏
@@JaenEngineering I read the equations and listened to relevant parts
Hi,
I would really enjoy if you can practically demonstrate the above circuit. you do that I will subscribe to your channel twice :)
Thanks Shakaib for watching and your interest in my channel 😄 . For more comprehensive Temperature Independent design pls see alternative technique in ua-cam.com/video/hFbnjbddUvs/v-deo.html which is a current generator circuit design using Zener Diodes, Op Amp and matched BJT Transistors.
awesome!
Thank you! Glad that you liked this video.
Interesting videos. Is it possible to use any dual-PNP package? Or it is necessary that datasheet contains magic word "matched"? Is it possible to use BC857BDW in SOT-363 package which contains dual PNP, but datasheet does not mention that they are matched. I would expect that every dual or quadruple BJTs in one package are on the same die and have basically the same characteristics.
Glad that you liked this video. The Matched PNP transistor pair requirement is to minimize temperature dependency by having practically same saturation current & thermal voltage for the two transistors. While you can use dual-PNP package, the thermal compensation won't be as good as the matched pair. For more comprehensive Temperature Independent design please see alternative technique in ua-cam.com/video/hFbnjbddUvs/v-deo.html which is a current generator circuit design using Zener Diodes, Op Amp and matched BJT Transistors. I hope this is helpful. 🙋♂️
Where do you find literature for your analog electronic circuits? I graduated applied electronics at my university but lot of the circuits you show here are unknown to me. I understand this is some designer advanced electronics but I am really curious about literature, I guess some books?
Thanks for your interest in my circuit design channel and videos. Glad that they are useful. These circuits are either my own designs or variations of existing circuits with additional customized tweaks and features. I am not using a very specific reference or text. That's why sometimes it takes a few days to come up with the next design video. For more analog circuits and signal processing examples see my Analog Video playlist: ua-cam.com/play/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt.html
That was very nice explanation.
The temp co of the pnp , are all pnp’s basically the same? What about tempco for vbe of npn transistors?
You are welcome. Glad that this video is useful. There is no NPN transistor in this circuit.
@@STEMprof yes, but my question was about npn tempco for vbe of npn transistor. I’ve seen many cases where this is used as a diode, where collector-base is shorted. I think it’s because of low leakage?
But I’ve also seen it used for temperature compensation, so I was wondering if the vbe of it was same as that for pnp (temp co, I mean)
@@yjweaver5108 For a given PN junction (whether in NPN or PNP transistor), the temperature coefficient is equal to roughly -2mV/Kelvin for a constant emitter current and PN junction temperature of 300°K (room temperature). That means the forward voltage of PN junction reduces nearly 2mV per 1°C increase in junction Temperature whether it is Base-Emitter of NPN BJT transistor or Emitter-Base voltage of PNP transistor. The main reason is that as PN junction temperature increases the reverse saturated current through emitter junction increases exponentially and hence PN junction voltage decreases according to the Shockley equation. Here are a few more related circuit examples: Temperature-Independent Current Circuit Design with Op Amp, BJT, Zener, Schottky Diodes ua-cam.com/video/hFbnjbddUvs/v-deo.html
Thermometer Circuit Design with Op Amp & BJT transistor ua-cam.com/video/55YsraFE0rg/v-deo.html
I hope this clarification is helpful.
@@STEMprof thanks, that answers my question