Difference between revisions of "Transistors"
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Transistors are just like Transformers. Only 5 letters difference. | Transistors are just like Transformers. Only 5 letters difference. | ||
| + | |||
| + | ==List== | ||
| + | * https://www.eevblog.com/forum/projects/why-transistor-vbe-drops-when-transistor-is-in-active-region-bc547-ibconstant/ Curve tracer question: Does Vbe change when Vce increases (on a BC547)? (Contrary to popular knowledge) | ||
| + | * https://www.eevblog.com/forum/projects/1-transistor-reset-oscillates-at-100s-mhz-why-(source-bob-pease)/msg5774519/#msg5774519 from troubleshooting analogue circuits by Pease, a transistor emittor follower on a microcontroller reset pin oscillates. | ||
| + | * https://www.eevblog.com/forum/projects/mosfet-rdson-test/msg5779201 - Using RDSon to test for fakes. | ||
| + | * https://www.tubesandmore.com/tech-articles/silicon-germanium-transistor-biasing-part5 - germanium transistors can have a leaky CE current which may bias it when otherwise a silicon transistor would not. I got the idea from a diodegonewild video. todo: buy / read some data sheets for germanium transistors | ||
==Transistor Building Blocks== | ==Transistor Building Blocks== | ||
[[Circuit_Building_Blocks]] | [[Circuit_Building_Blocks]] | ||
| + | |||
| + | ==Basics== | ||
| + | ===NPN and PNP=== | ||
| + | * NPN Never Points In | ||
| + | * PNP Points In | ||
| + | The emitter is always the errow. | ||
| + | |||
| + | It's all about the bass. The diode test will work whichever way the errows point to. (i.e. npn will conduct base to emitter, and base to collector, pnp will conduct emitter to base, and collector to base). | ||
| + | |||
==Tips/Techniques== | ==Tips/Techniques== | ||
===Darlington Transistors have Internal Resistors=== | ===Darlington Transistors have Internal Resistors=== | ||
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* https://forum.allaboutcircuits.com/threads/measuring-mosfets-rds-on.181819/ | * https://forum.allaboutcircuits.com/threads/measuring-mosfets-rds-on.181819/ | ||
* http://web.archive.org/web/20220127031735/https://www.engineersgarage.com/testing-mosfet-part-16-17/ | * http://web.archive.org/web/20220127031735/https://www.engineersgarage.com/testing-mosfet-part-16-17/ | ||
| − | It's possible, but be aware of what voltage your meter outputs, | + | It's possible, but be aware of what voltage your meter outputs, what is required for conduction, and what resistance to expect. |
| + | ===Gate and Source on a JFET are 'sometimes' interchangeable=== | ||
| + | I was looking at this data sheet for a repair (nte312): https://www.digikey.com/en/htmldatasheets/production/5439610/0/0/1/nte312 | ||
| + | And saw this note at the end. | ||
| + | This is discussed in forums online. Stack exchange and eevblog... | ||
| + | * https://www.eevblog.com/forum/chat/are-jfet-drain-and-source-interchangeable/ | ||
Latest revision as of 12:49, 20 September 2025
Transistors are just like Transformers. Only 5 letters difference.
List
- https://www.eevblog.com/forum/projects/why-transistor-vbe-drops-when-transistor-is-in-active-region-bc547-ibconstant/ Curve tracer question: Does Vbe change when Vce increases (on a BC547)? (Contrary to popular knowledge)
- https://www.eevblog.com/forum/projects/1-transistor-reset-oscillates-at-100s-mhz-why-(source-bob-pease)/msg5774519/#msg5774519 from troubleshooting analogue circuits by Pease, a transistor emittor follower on a microcontroller reset pin oscillates.
- https://www.eevblog.com/forum/projects/mosfet-rdson-test/msg5779201 - Using RDSon to test for fakes.
- https://www.tubesandmore.com/tech-articles/silicon-germanium-transistor-biasing-part5 - germanium transistors can have a leaky CE current which may bias it when otherwise a silicon transistor would not. I got the idea from a diodegonewild video. todo: buy / read some data sheets for germanium transistors
Transistor Building Blocks
Basics
NPN and PNP
- NPN Never Points In
- PNP Points In
The emitter is always the errow.
It's all about the bass. The diode test will work whichever way the errows point to. (i.e. npn will conduct base to emitter, and base to collector, pnp will conduct emitter to base, and collector to base).
Tips/Techniques
Darlington Transistors have Internal Resistors
See also: (sziklai vs. darlington)
https://circuitcellar.com/resources/darlington-vs-sziklai-pair/
Never Trust Data Sheets Power Mosfet ratings
https://www.eevblog.com/forum/projects/50w-really/msg5449229/ Perhaps I should have a page just for traps in data sheets.
Measuring R(ds)ON of an N-FET with Two Meters
- https://forum.allaboutcircuits.com/threads/measuring-mosfets-rds-on.181819/
- http://web.archive.org/web/20220127031735/https://www.engineersgarage.com/testing-mosfet-part-16-17/
It's possible, but be aware of what voltage your meter outputs, what is required for conduction, and what resistance to expect.
Gate and Source on a JFET are 'sometimes' interchangeable
I was looking at this data sheet for a repair (nte312): https://www.digikey.com/en/htmldatasheets/production/5439610/0/0/1/nte312 And saw this note at the end. This is discussed in forums online. Stack exchange and eevblog...
