Common Collector Amplifier - Practical Build (2/2)

[@hedleyfurio]

Your format of theoretical discussion first , followed by simulation , followed by lab work is excellent and should be the standard for any educational presentation - many thanks for all the hard work and valuable resource 👍👍👍

[@Cynthia_Cantrell]

This type of amplifier is very helpful for high-impedance sensors. One thing to watch out for though is that it has a very low PSRR (Power Supply Rejection Ratio). So if you want to keep a clean signal through this, you must ensure you also have a very clean power supply rail for it.

[@georgesampson4714]

Every time I watch a video like this I gain a little more insight into how an engineer thinks about a problem. Unfortunately the saying "It's hard to teach an old dog new tricks" seems to be true in my case. But I think I'm making progress so keep up the fine work you are doing.

[@biswajit681]

Hi could you please cover linear and switching power stability using bode plot in LTspice.Its nowhere present over internet..it would be a great help

[@biswajitsingh7470]

Yes this topic is very much needed...it's hard to understand and only @fesz can clear the concept 😉

[@R2AUK]

Nice video. However 8:50 you can't measure the output impedance of the amplifier the way you did. What you are measuring is the input impedance of the output port which is not the same as output impedance. This may be true for passive devices (LC filters, etc) but not active components.

[@FesZElectronics]

How would you propose a better method? I could try it some time and compare results.

[@R2AUK]

@@FesZElectronics you can estimate the output impedance by loading the amplifier to R1 first and then to R2. For each resistance the amplitude Vi of the output signal should be measured (for a constant input signal; the amplifier should not be in compression). Then the output impedance can be determined as (R1 - R1*(V1/V2)) / (V1/V2 - R1/R2). This method can also be used in LTspice. Naturally this is applicable only to linear (class A) amplifiers. For other classes the output impedance strictly speaking is not determined (it may be - for class C/D amplifier followed by a filter, however).

[@boatknuckle]

@@FesZElectronics Agreed. That won't work for measuring output impedance. W2AEW has an excellent video on his channel about how to use a nanoVNA to measure the input and output impedances of a small-signal amplifier. As he also points out, one must be careful when measuring input impedance to not drive the transistor into a non-linear region -- which the nanoVNA will do if not attenuated. PS: Love your videos, I look forward to each new one and have learned a lot. Keep up the great work!

[@boatknuckle]

W2AEW video kzbin.info/www/bejne/bYXXfHhpbrmKpqs

[@dannyperry8070]

Great videos. Any way of getting the pcb files? These are perfect for experimenting. THANKS

[@stuferg5801]

Hello, I want to design a buffer for a wide band rf vco, which operates over several decades of frequency up to about 200MHz. Both common collector bjt amplifiers and jfet amplifierd have a shunt input capacitance, which causes the input impedance to drop dramatically at ‘high’ frequencies. ... What methods are used to buffer high frequency oscillators above a few MHz ?

[@barrymayson2492]

Hi not sure if this suggestions any good but I have used MMIC to buffer rf oscillators they have pretty good response over a wide band width. You can even get small boards ready made from china but they are easy to make and require very few additional components.

[@dannyperry8070]

Fantastic video's. I have watched them at least three times. Any way of getting the PCB files for the lab you put together. Thanks

[@FesZElectronics]

I usually share design files above a certain level of Patron support.

[@dannyperry8070]

@@FesZElectronics Just signed up on Patron. Thanks

[@Mike-H_UK]

Great video. Many thanks!

[@benatesnaola6001]

Great!!

[@electengin820]

tnx

[@arabeagle7591]

Use You tube settings under caption option you can translate the video

[@pa4tim]

Great video, thanks. Can you do a video on bode plots. I still struggle with them. I have a book about it but that is al about the math, and math is not my forte

[@FesZElectronics]

Do you mean the usage of Bode plots for power supply stability, or just in general? Maybe you have some example on where you would need to use these?

[@pa4tim]

@@FesZElectronics Just in general. I have a scope that has this option but I never tried it. I mostly repair testgear so no need for bode plots but by co-incident I just build a small sub-woofer amp and it would be fun to do a bode plot to see the gain and fase response. However as a check for power supplies this sound very interesting :-)

[@bob_mosavo]

Thanks 😁