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You can find many very circuit ideas at ePanorama.net circuits page.
In addition to this links to interesting electronics design related articles worth to check out can be posted to the comments section.
1,935 Comments
Tomi Engdahl says:
https://en.wikipedia.org/wiki/Common_base
https://www.quora.com/Why-the-common-base-amplifier-is-not-commonly-used-as-an-audio-amplifier
Tomi Engdahl says:
https://www.electronics-tutorials.ws/power/unijunction-transistor.html
Tomi Engdahl says:
https://www.edn.com/a-negative-current-source-with-pwm-input-and-lm337-output/#google_vignette
Tomi Engdahl says:
https://www.ic-components.com/blog/comprehensive-analysis-and-applications-of-the-7805-voltage-regulator-ic.jsp
Tomi Engdahl says:
https://en.wikipedia.org/wiki/TL431
Tomi Engdahl says:
https://www.edn.com/a-high-performance-current-source/#google_vignette
Tomi Engdahl says:
https://www.edn.com/pwm-programmed-lm317-constant-current-source/#comment-33041
Tomi Engdahl says:
https://www.newtoncbraga.com.br/banco-de-circuitos/22582-teste-de-cristais-cir3594.html?fbclid=IwY2xjawJeN-9leHRuA2FlbQIxMQABHuLF_B-zV7qIP6pGbcrfXG9tdnFKHCWnXE5kY1AZbMi9Po2S3j4Pw85koOqr_aem_uokOMsH1p1yWn1SHvanwpw
Tomi Engdahl says:
WIMA in Mannheim has discontinued the production of MKS capacitors!
( https://www.diyaudio.com/community/threads/wima-mks-and-more-caps-discontinued-eol.425402/ )
Tomi Engdahl says:
https://www.edn.com/another-simple-flip-on-flop-off-circuit/#google_vignette
Tomi Engdahl says:
https://www.edn.com/did-you-put-x-and-y-capacitors-on-your-ac-input/#google_vignette
Tomi Engdahl says:
https://www.planetanalog.com/a-short-primer-on-x-and-y-capacitors-in-ac-power-supply/
Tomi Engdahl says:
https://www.edn.com/lm4041-voltage-regulator-impersonates-precision-current-source/
Tomi Engdahl says:
https://hackaday.com/2025/04/21/biasing-transistors-with-current-sources/
Tomi Engdahl says:
https://www.edn.com/a-closer-look-at-a-capacitor-auto-discharge-circuit/
Tomi Engdahl says:
https://www.edn.com/field-analyzers-gain-vector-functions/#google_vignette
Tomi Engdahl says:
https://www.edn.com/seven-octave-linear-in-pitch-vco/
Tomi Engdahl says:
https://www.edn.com/mram-and-reram-the-quest-for-automotive-aerospace-niches/
Tomi Engdahl says:
OKI Reaches New Heights With a 124-Layer PCB
May 09, 2025 by Luke James
The 124-layer printed circuit board surpasses the longstanding 108-layer industry ceiling without increasing the standard board thickness of 7.6 mm.
https://www.allaboutcircuits.com/news/oki-reaches-new-heights-with-124-layer-pcb/
Tomi Engdahl says:
https://www.edn.com/precision-programmable-current-sink/
Tomi Engdahl says:
https://www.newtoncbraga.com.br/projetos/18364-filtro-de-60-hz-art2191.html?fbclid=IwQ0xDSwKFV4ZjbGNrAoVXg2V4dG4DYWVtAjExAAEeXw6JgYl1sVO7ZbuLUztz5aMfoRtbKswK6qbWjECZywMsox4KGPUwQZJUMcA_aem_j0WnxuW14OKVEEutwPDsbg
Tomi Engdahl says:
https://audiovideo.fi/opas/mosfettipaate-mauri-pannari-ja-mika-rintala/
Tomi Engdahl says:
http://cappels.org/dproj/simplest_LED_flasher/Simplest_LED_Flasher_Circuit.html?fbclid=IwQ0xDSwKfgitjbGNrAp-CF2V4dG4DYWVtAjExAAEemv7u_EiBzIMpSSevzxkoVdkpV8ZHywJ75HTUPwfYbZf-KBOF8PvXsj3gOzw_aem_a18V4N1t09HD94V38ZR2wA
Tomi Engdahl says:
https://solderingmind.com/simple-rain-detector-alarm-circuit/#google_vignette
Tomi Engdahl says:
https://www.edn.com/a-two-way-mirror-current-mirror-that-is/
Tomi Engdahl says:
https://www.hackster.io/news/miniature-attiny-led-probe-f97876fa8eff
Tomi Engdahl says:
Led voltage indicator
https://youtu.be/MHp1QqaaNd0?si=7rI2iBtIlwkkZXMB
Tomi Engdahl says:
https://etn.fi/index.php/tekniset-artikkelit/17700-afe-tehopiireissae-ratkaisee-oikea-tasapaino
Tomi Engdahl says:
https://www.elektormagazine.com/news/circuit-a-diy-pcb-short-finder?fbclid=IwQ0xDSwLsYU1jbGNrAuxhLmV4dG4DYWVtAjExAAEerSoAB7wGk_dtreuv1NpEO4kBAu0rjTffNSpEYR4FQpOytnYEhOyj7XWYDa4_aem_2g0i_B9aa1E20ZzaC3WlTA
Tomi Engdahl says:
https://hackaday.com/2025/08/04/the-scourge-of-fake-retro-components-like-unijunction-transistors/
For example, while programmable unijunction transistors (PUTs) like the 2N6028 are still being manufactured, they cost a few dollars a pop in low quantities. UJTs used to be common in timer circuits, but now we have the 555
there was no real reason to specify a UJT when a combination of a PNP and an NPN transistor could do the same job, and be more repeatable. I have used this circuit several times since.
https://www.instructables.com/Circuit-Collection-of-the-Programmable-Unijunction/
+3.
…an extremely valuable piece of component-knowledge and circuit-design and which most people have forgotten—if they ever knew it (and, yes: there are very many situations where a UJT and / or PUT is the only correct, elegantly simple solution).
Many thanks for the refresher.
Three ‘thumbs-up’.
A unijunction transistor can be used to make a simple oscillator whose frequency can be set by a single resistor (or capacitor). So we have many 1970s circuits for electronic organs using a unijunction, a capacitor, and some resistors. The original Stylophone worked that way, I think. Add another bipolar transistor in a fixed-frequency phase-shift oscillator configuration for vibrato. I built an organ like this myself, probably from a schematic in a Babani book.
Now that I think about it, Everyday Electronics magazine published an electronic bagpipes project using unijunction transistors.
May 1974 issue of Everyday Electronics: https://www.worldradiohistory.com/UK/Everyday-Electronics/70s/Everyday-Electronics-1974-05.pdf
Original Stylophone pocket synthesizer used a UJT for the oscillator. Another transistor for driving the speaker, and another for vibrato. THREE transistors total. Beat that haha.
Also, a UJT osc has a spikey waveform, rich in harmonics, unique sound.
I’ve only used UJT’s as pulsed gate drive for big SCR’s, or xenon strobe lights, or the Jana mosquito repeller.
Tomi Engdahl says:
https://hackaday.com/2025/08/05/2025-one-hertz-challenge-shoulda-put-a-ring-oscillator-on-it/
Tomi Engdahl says:
https://hackaday.io/project/203645-one-hertz-sculpture
Tomi Engdahl says:
https://hackaday.io/project/176107-led-coupled-logic-lcl