Comments on: The Common-Collector Amplifier Input and Output Resistance – The Proof https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/ Electronics Design and Modeling with Emphasis on Analog Design Sun, 28 Apr 2019 02:26:06 +0000 hourly 1 By: Adrian S. Nastase https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/#comment-45016 Sun, 28 Apr 2019 02:26:06 +0000 http://masteringelectronicsdesign.com/?p=814#comment-45016 In reply to garcia.

“I to understand microelectronics. I also think that including the source resistance in the output impedance of the amplifier could be misleading.”
No, it is not. When learning about these simple amplifiers one needs to know that the output impedance depends on the source.

]]> By: garcia https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/#comment-44741 Sat, 06 Apr 2019 11:25:52 +0000 http://masteringelectronicsdesign.com/?p=814#comment-44741 I to understand microelectronics. I also think that including the source resistance in the output impedance of the amplifier could be misleading.
1) Isn’t the purpose of the input and output resistances to interface the amplifier with the other blocks so as to to predict the real gain.
If one include the source in the output impedance and the load in the input impedance there is no point in calculating them.

But more importantly, as one goal of the common collector is to adapt a high input impedance from a previous stage (ex: common emitter) to a low output impedance, there is no reason to assume that Rs (=the output impedance of the previous stage) will be small even if it appears divided by beta in the calculation of Ro.

For exemple, imagine a

]]> By: Jay panchal https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/#comment-43345 Wed, 26 Sep 2018 18:08:26 +0000 http://masteringelectronicsdesign.com/?p=814#comment-43345 Easy to understand article. Thanks again!!!

]]> By: Adrian S. Nastase https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/#comment-33829 Sun, 06 Mar 2016 22:28:53 +0000 http://masteringelectronicsdesign.com/?p=814#comment-33829 In reply to haritha.

In this article I deduct the input resistance of the common-collector circuit. It is the last equation. The paragraph before the last explains why: “This equation shows that the common-collector amplifier has a large input resistance, due to the product (?+1) RE.” And then it says that if RE is 1k and ?+1 is at least 200, you end up with a large input resistance of at least 200k.

]]> By: haritha https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/#comment-33700 Mon, 29 Feb 2016 16:25:19 +0000 http://masteringelectronicsdesign.com/?p=814#comment-33700 why cc has high input resistance

]]> By: Gabriel https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/#comment-10978 Sun, 03 Feb 2013 15:40:08 +0000 http://masteringelectronicsdesign.com/?p=814#comment-10978 i thought this have been very helpful. thanks! 😀

]]> By: Adrian S. Nastase https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/#comment-4038 Wed, 14 Sep 2011 07:13:12 +0000 http://masteringelectronicsdesign.com/?p=814#comment-4038 In reply to Matthew.

Yes, it will come soon. Keep an eye on MasteringElectronicsDesign.com. Thank you for visiting.

]]> By: Matthew https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/#comment-4033 Tue, 13 Sep 2011 20:16:24 +0000 http://masteringelectronicsdesign.com/?p=814#comment-4033 How about the same type of analysis for the common-base amplifier please?

]]> By: doug https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/#comment-3205 Thu, 10 Mar 2011 09:09:35 +0000 http://masteringelectronicsdesign.com/?p=814#comment-3205 thank you for your reply, and apologies for the earlier typos,
as you say, stray capacitances are proving to be a major consideration, ive noticed even on fairly low frequencies, a few hundred kilohertz or so, and with even a 555 on a good layout, im getting a residual capacitance of around 15 p to 20 p on the timing elements.

thanks again
dougal

]]> By: Adrian S. Nastase https://masteringelectronicsdesign.com/the-common-collector-amplifier-input-and-output-resistance/#comment-3202 Thu, 10 Mar 2011 01:31:15 +0000 http://masteringelectronicsdesign.com/?p=814#comment-3202 In reply to doug.

Yes, although, for high frequency applications, I would add the transistor parasitic capacitances in this hybrid-pi model. At minimum, add C-pi in parallel with r-pi and the feedback capacitance C-miu.

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