Measuring the Input Impedance of a Product, Circuit or System (070a) 

I'm glad you found it helpful ... and refreshing ;-)

Thank you very much for your service to your country! I was in the U.S. Air Force. Enjoy! 🙂

Thank you! 🙂

You are welcome! 😁😁😁😁😁😁

Thank you! Yeah, the higher frequency stuff is a LOT trickier! As an adjunct to this, there is my video on measuring non-50 Ohm stuff with a 50 Ohm VNA. 🙂 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-dgDS4rjb-GU.html

LOL!🤣 TMB!! I gotta use this! Thanks! 🙂

Thank you so much! ... and you are very welcome! 🙂

If you take in my video on measuring non-50 Ohm things using a 50 Ohm VNA (ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-dgDS4rjb-GU.html) you will see that I am in agreement. If we absolutely do not know what the input impedance is, where do we begin and how do we accommodate this? An initial measurement without impedance matching gives us a ballpark. From this ballpark, how precise do we need to be? Many times this ballpark is sufficient, but not always. Then we have to turn to impedance matching business. In my next video I do NOT do impedance matching because the amplifier I will be testing the input impedance of is SUPPOSED to be in a 50 Ohm system, though it turns out ... not so much. 🙂

You are welcome! 🙂

Thanks, man! I had to think about this a little... yeah, negative feedback with a capacitor in parallel with it to limit high end ... that would certainly do it. I agree with you on the fixed high input Z first stage; put the volume control between the first stage and the next. That is how I did it in my mixer project (Design End-to-End series). He is the reason I am here, my friend. That is my wallpaper on my desktop. 🙂

@@eie_for_you I'm completely with you, my friend - in my 'retirement' I'm an adjunct college prof, teaching engineering technology. While I'm not allowed to openly discuss my faith, I subtly include Christian values in the lectures and talk about the importance of integrity in the industries where they will likely work. Young people need to hear this from an old guy like me, as the rest of what they are constantly bombarded with is just the opposite.

@@carlosanvito May 21, 2011 was the beginning of judgement day on the world And it shall come to pass in that day, a great tumult from the Lord shall be among them; and they shall lay hold every one on the hand of his neighbor, and his hand shall rise up against the hand of his neighbor. Zechariah 14;13 "Tumult" = confusion & disbelief ...on purpose, by design for the punishment of mankind! Division is the result. Babylon is fallen(world systems). Division is worldwide in religions, politics, economics, news, industry, sciences, sports, medicine, entertainment, and even between the sexes. ...have you followed world events lately? The Lord is known by the judgement which he executeth, the wicked is snared in the work of his own hands. Higgaion. Selah. Psalm 9;16 Whoso keepeth the commandment shall feel no evil thing, and a wise man's heart discerneth both time and judgement. Ecclesiastes 8;5 And the seventh angel sounded; and there were great voices in heaven, saying, The kingdoms of this world are become the kingdoms of our Lord, and of his Christ; and he shall reign to ever and ever. And out of his mouth goeth a sharp sword, that with it he should smite the nations: and he shall rule them with a rod of iron: and he treadeth the winepress of the fierceness and wrath of Almighty God. Revelation 11;15 19;15 spoiler alert: The biblical calendar has been known, published(1974), and carefully studied for half a century now... There are forty+ time-paths from the bible pointing to 2033 as the last day. Go look up: Ebible2 timelines T - minus 9 years and counting... That is what young people need to know, Carlos FEED MY SHEEP

@@carlosanvito Because I have called, and ye refused; I have stretched out my hand, and no man regarded; But ye have set at nought all my counsel, and would none of my reproof: I also will laugh at your calamity, I will mock when your fear cometh. Proverbs 1; 24-26 GOD is our refuge and strength, a very present help in trouble He looketh on the earth, and it trembleth: He toucheth the hills, and they smoke. Psalm 103;32 Bow thy heavens, O lord, and come down: touch the mountains, and they shall smoke. Psalm 144;5 READ THE BOOK ! And an highway shall be there, and a way, and it shall be called the way of holiness; the unclean shall not pass over it; but is shall be for those, the wayfaring souls, though fools, shall not err therein. Isaiah 35;8

@@carlosanvito So very true! They've heard the message of "me first at all costs" ... "it is all about me and what I need" so much that selflessness is a rarity. 😞 Lying is OK if it is "for a good cause" (usually their own). Yes, integrity is so important. Keep up the good work! 🙂

Check out this video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-bPmtIVmlJok.html 🙂

I'm glad you liked the video! You made me think ... I thought for sure I said to turn on the little amplifier ... yup, at 10:29. 🙂

Yes, you are right. This signal generator has a fixed 50 Ohm output impedance. However, there is a setting for the channel which we can set to the impedance that it will see on outs output which corrects the voltage as indicated on the display to accommodate the load impedance that actually exists on its output. It doesn't change the actual output voltage. It changes the voltage as *indicated* on the display. With that said, I DO personally own a signal generator whose output impedance is NOT 50 Ohms. While it is a good bet that most mainstream signal generators output impedance is 50 Ohms, it certainly in not a given. There is a whole class of them, for instance, which are 600 Ohms and 75 Ohms. So, let's be careful about our assumptions. 🙂

@@eie_for_you That's right, that's why I wrote “All signal generators I know”. But that wasn't right either, because I have an old Wien-Robinson oscillator that I hadn't thought of, whose output impedance I don't know. But I doubt that it has 50 ohms.

@@egonotto4172 True that! It is a good assumption, in general, that all signal generators of modern design will have an actual output impedance of 50 Ohms unless they have some specialized purpose. The cable TV industry is all about 75 Ohm as is the CCTV because 75 Ohm coax has less loss than their 50 Ohm counterpart. Parts of the audio industry was all about 600 Ohms; that is where the whole dBu steps in (1 mW into 600 Ohms is 0 dBu). 🙂