Corrections needed on page /vol_3/chpt_4/8.html

Discussion in 'Feedback and Suggestions' started by keithostertag, Oct 28, 2012.

  1. keithostertag

    Thread Starter Member

    Oct 4, 2012
    48
    2
    Hi-

    I believe there are a few problems with page /vol_3/chpt_4/8.html, "The Cascode Amplifier".

    First, in a figure in the middle of the page (03502.png) depicting two schematics, one labeled "Cascode" and the one next to it on the right labeled "Common-base". That schematic on the right should be labeled "Common emitter" instead, and the title for that figure relabeled appropriately.

    After that things get a little confusing. The following graph shows two plots, one for the cascode and one for the common-emitter. The SPICE code that follows has no statements for plots for either one. The text says that code is for "printing AC input and output voltages", but contains no print statements.

    Also, it is confusing to show two different schematic diagrams drawn seperately for "comparison", but then state that they share a voltage source ("The AC source V3 drives both amplifiers via node 4") and give SPICE code that includes both. Hmmm... why not draw the schematic as one complete unit? Or present SPICE code for each schematic separately? Imho, it's confusing as is. The only thing I can think is that it has been done that way to conserve space and possibly some redundacy, but I feel it is done at the expense of clarity.

    Then, the hyperlink at the end of this sentence:

    "The bias resistors for this circuit are calculated in an example problem cascode."

    points to itself, not to some separate example showing calculations.

    Hope this is helpful.

    Keith Ostertag
     
  2. keithostertag

    Thread Starter Member

    Oct 4, 2012
    48
    2
    I now see that the hyperlink is meant to point to the entire discussion, specifically three paragraphs above. I initially thought it meant to point to some additional discussion on a different page.
     
  3. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    On first glance, your remarks seem sound, but I 'd like someone more of an expert than me on the topic to call it.
     
  4. keithostertag

    Thread Starter Member

    Oct 4, 2012
    48
    2
    Also, this statement: "The pn2222 datasheet list Ccbo = 8 pF.[FAR]" points to itself, I would have thought it should point to a datasheet. Also, I can't find how Ree was initially described/defined. This statement: "For details on the 26Ω, see “Derivation of REE”, see REE. " Evidently refers to this statement on the same page, just above: "The emitter current is set to 1.0 mA by biasing. REE= 26mV/IE = 26mV/1.0ma = 26 Ω." But where did that 26mV come from? I do seem to recall a diagram showing Ree, but in moving back several pages was unable to relocate it. I gotta say, I really enjoy these tutorials and learn a lot from them. I am only trying to help in making them better. I'm using ngspice, which has a slightly different syntax than what these pages use, so sometimes that gets in my way of understanding the SPICE codes. Thanks for your help, Keith Ostertag
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Just remember, this is meant to be a paper book. No hyperlinks are appropriate, though they can exist.

    I'll try reviewing, but I suspect I would like a better opinion than mine too.
     
  6. keithostertag

    Thread Starter Member

    Oct 4, 2012
    48
    2
    Reading further, I see that the 26mV for Ree is explained in detail in a later page.
     
  7. sailorjoe

    Member

    Jun 4, 2013
    361
    63
    I just read the chapter on Cascode Amplifiers, and wanted to provide some feedback for corrections, so I joined the Forum and found these remarks. I can confirm that all the comments provided by Keith were the same things I noticed and wanted to point out. The circuit on the right of the second figure is indeed a Common Emitter configuration, for example.
     
  8. LDC3

    Active Member

    Apr 27, 2013
    920
    160
    The figure in the middle is not correct if the figure at the top is correct. The caption for the middle figure has cascode on the left, but it doesn't look like the cascode in the top figure. Also the label for common base on the right has a common emitter configuration.
     
  9. sailorjoe

    Member

    Jun 4, 2013
    361
    63
    I believe the left side middle figure is a correct cascode configuration. You have to redraw Q2 and its connected components to see it, plus there are more biasing voltages in the middle circuit, but its a good circuit. Correct on the middle circuit on the right.
     
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