Thermometer Sensor Circuit Explained with Op Amp and NPN Transistor

[@LousyPainter]

Excellent content!

[@STEMprof]

Thank you! Glad that this video is useful. For more sensor circuits & amplifiers please see ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj a

[@shakaibsafvi97]

Hi,
Was waiting for this ..... Cheers !!!

[@STEMprof]

You are welcome! Thanks for your interest in my videos. Please see more sensor circuit videos in ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj which is sensor video playlist.

[@Chupacabras222]

Very interesting. Thanks for valuable content. I like the "trick" with those 2 zeners :)

[@STEMprof]

You are welcome 🙏 Glad that you like this video and the technique of series of two Zener Diodes that counteract their temperature dependencies. 🙋‍♂️

[@whatever3041]

Hi, I love your videos, can you please make a very thorough video on BJT CE amplifier. Thanks 🙏

[@STEMprof]

You're welcome! Glad that this channel is useful. Sure, regarding BJT Amplifier please see:
Class A BJT Amplifier Design with Transformer ruclips.net/video/gKlJrqGqeCI/видео.html
Differential Amplifier Design with BJT & JFET transistors ruclips.net/video/zKgSYvk7JAM/видео.html
Feedback Amplifier: How to find DC Bias and AC Gain ruclips.net/video/6dLMxpLNKv4/видео.html
How to find Gain of Feedback Amplifier Example with JFET & BJT Transistors ruclips.net/video/NB1-mYglXsY/видео.html
I hope these videos are helpful. 🙋‍♂️

[@STEMprof]

Thermometer Sensor Circuit Operation is explained in this video. For more sensor amplifiers see ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj and the following videos
EKG ECG Amplifier with Right Leg Drive Explained ruclips.net/video/1c7KGXPs4do/видео.html
Thermometer Circuit Design with Op Amp and BJT transistor ruclips.net/video/55YsraFE0rg/видео.html
PhotoDiode Amplifier with Data Compression Explained ruclips.net/video/hqrRx2ufAwg/видео.html
Thermometer Current source ruclips.net/video/Ggf0yCaTTiY/видео.html
Strain Gauge Wheatstone Bridge Instrumentation Amplifier Explained ruclips.net/video/io1yBcCsP-Y/видео.html
Temperature-Compensated Programmable Current Source Circuit Design with Zener Diode, BJT Transistors ruclips.net/video/QY48IQXJIRI/видео.html
Temperature-Independent Current Circuit Design with Op Amp, BJT, Zener, Schottky Diodes ruclips.net/video/hFbnjbddUvs/видео.html
Instrumentation Amplifier with Electronic Gain Control ruclips.net/video/C4tghZ-q6Zs/видео.html
For more analog circuits and signal processing examples see: ruclips.net/p/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt
I hope these sensors and thermometer circuits videos are interesting. 🙂

[@byronwatkins2565]

Actually, 4.3(0.055%)-3.9(0.06%)=0.0025% so V = 8.2V(1+0.0003% (T-25C)). Also, by varying the Zener current we could even trim this out to have zero temperature coefficient.

[@STEMprof]

Well said! Thank you for the follow-up accurate calculation of the overall temperature coefficient for the series of two Zener Diodes described in the video. The Zener current adjustment is best done via using a Potentiometer instead of the fixed 1k Ohm resistor. For an alternative Temperature sensor design technique pls see Thermometer Circuit Design with Op Amp and BJT transistor ruclips.net/video/55YsraFE0rg/видео.html

[@alexloktionoff6833]

Can two zeners be replaced with a single TL431 ?

[@STEMprof]

That's a good question. Yes, you can as long as the precision reference voltage is set so that it's temperature variation is negligible compared with -2.1mv per degree voltage change of PN junction. Otherwise, more precise Shunt Voltage Regulator is recommended.

[@shakaibsafvi97]

-15V required :(

[@STEMprof]

-15v is not required. You can change it to -10V and reduce 1k Ohm to say 470 Ohm. Or alternatively we can design the same circuit using +15V instead of -15V. Here is also an alternative implementation: Thermometer Circuit Design with Op Amp & BJT transistor ruclips.net/video/55YsraFE0rg/видео.html

[@TeslaFactory]

Could snap ground for +15V and snap-15V for ground to get the same potential difference, non?

[@STEMprof]

From Voltage difference perspective, yes but we won't then get zero volt at output when PN junction temperature is zero degrees Celsius. We will need a level shifter or further circuit modification.