Comparing bipolar NPN or PNP transistors directly: a test circuit + schematic and demo HD

A simple circuit to compare Bipolar transistors. Here I showed the comparison of two BC 547 b NPN Silicon transistors, each with a Hfe =current amplification of say 300. But of course you can compare a “known” transistor with an “unknown” transistor, of course both of them must be NPN in the showed setup/schematic. You can test PNP transistors when you reverse the + (plus) and the – (minus) to the test circuit and in that case you can compare two PNP Bipolar transistors, be it Germanium or Silicon. Of course it is not possible with this circuit & setup to compare at the same time a PNP and a NPN bipolar transistor on say on their amplification factors. Furthermore: the way of testing is elementary and to compare HF transistors or High Voltage transistors you have to send in/use a quite high voltage and/or a quite high frequency and, with HF circuits, you will probably need a real & typical HF setup. The showed circuit & demo will work up to 15 MHz. There is a “known” transistor, be it PNP or NPN, LF or HF type in this way of testing/comparing. Of course you can test/compare a NPN Germanium transistor with a NPN Silicon transistor or a PNP Germanium transistor with a PNP Silicon transistor. Be sure to turn the bias (working & operation point) potentiometer (22 K or 25 K) to see the comparative results in amplification, noise, etc. (!) Please note: here I have compared two common all purpose (BC 547 b) NPN Silicon transistors. NPN is, by the way, the most common, since the 1980’s. The very early transistors of the (say) 1950’s and early 1960’s were often Germanium PNP transistors. All the videos hat I have published on You Tube can be found via my Channel Trailer: Link is https://youtu.be/xbgQ8T3oqh4 In thematic order you can find these video’s under the “comments” section. Important: to find all the links to the (+/-700) video’s on my YT Channel, select, in the comments section, “NEWEST FIRST” My books about electronics are available via the website from “Lulu”, search for author “Ko Tilman” there. https://www.lulu.com/shop/search.ep?keyWords=ko+tilman&type= There is an important video via which you can buy a document where I give links to many of my video’s, published between 2010 and 2018. Link is: https://youtu.be/XXRsA24NUE0 My books are also available via Barnes and Noble and via Amazon. Regarding all my video’s: I constantly keep them actual, so the original video’s with the most recent information are always on YouTube. That is the source, and search there. When my video’s are reproduced or re-edited on other websites/channels you can not (!) be sure about the original content (=really working electronics with real properties for a purpose) and important adaptations to the circuits. Be aware of that, I saw on the internet my circuits reproduced in a poor or not proper way. I also found that people probably republish my circuits under phantasy names and/or with phantasy properties. Sometimes they want to