Excel-based transistor amplifier calculator

in techniques by DP | 7 comments

resistor_given

Paulo shared an Excel-based transistor amplifier calculator.  ‘Besides the basic gain and biasing calculations many others implement, this calculator can also estimate noise which is a bit more involved':

..Because this is a circuit I use frequently, I decided to make an Excel spreadsheet to ease the calculations. The spreadsheet started as a simple resistor value calculator (given a bias point) and later evolved to include some more advanced features such as noise estimation. I decided to share this spreadsheet in this article in hopes it will help other Electronics enthusiasts in these same tasks..

Via the contact form.

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Comments

  1. Michael says:

    This is great but it doesn’t render to a readable form in Open Office…

  2. Drone says:

    Yeah, the spreadsheet is in .xlxs format, Micro$oft Office only – and the later versions only too. Sigh… Too bad, the screen shots look like this is pretty nice.

    I think the standard is to save in Office 2003 format for most compatibility. But even then, although LibreOffice can open and save in Excel 2003 format, I don’t think the macros are compatible. So that may not work.

  3. Paulo says:

    Hi, I’m the author. Thanks for your feedback. I added an Excel 2003 version to the article. There is no macro/VBA code in the spreadsheet as even for the integration I used Excel’s native functions as much as possible. Hopefully you can open this version.

    Paulo

    • Drone says:

      Woo Hoo! I just opened the newest version in Excel 2003; looks great! When I get home later on I’ll try it in the latest version of LibreOffice and post back. I’m not sure how much of the fancy and colorful formatting and graphic content will move over to LibreOffice.

      By the way, LibreOffice is also available in a portable version (no install required) for Windows from the guys over at PortableApps dot com.

      Thanks a lot Paulo, nice work!, David (Drone)

      • Drone says:

        Hi Paulo,

        Sorry for the late reply… I found the Excel 2003 compatible .xls version of the transistor amplifier spreadsheet works just fine in LibreOffice 4.0.0.3 running in WindowsXP SP3+ as of 31 March 2013. Everything looks and works as it does in Excel 2003.

        By the way, it seems your frequency response does not take into account a working load impedance. You have the output capacitor connected to ground. In reality this would not be the case, the output capacitor would be in series between the collector and a load impedance to ground. In this role, the capacitor acts as a DC block. You need to take the load impedance into account when calculating frequency response. One assumption would be to assume a purely resistive load which equals the output impedance of the amplifier to facilitate maximum power transfer. But obviously that’s not always the goal.

      • Paulo says:

        Hi Drone,

        Actually there is a load impedance in the “noise” tab (called RL). If you are talking about the first two tabs, then yes, I assumed a very high impedance relative to the Zo of the circuit which holds true for many applications. Otherwise, just replace Zo with ZO//RL and it will calculate the correct LP frequency. Put another way, f3dB LP ~= 1/(2*PI* (RL//Zo)*CL) for low frequency applications. For high frequency, you need a more complex model of the transistor.

        Paulo

  4. Michael says:

    Thanks Paulo!
    It now renders perfectly, you’re the best!

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