Week #10: (11/9-13) Characteristic Curves, dB & Gain

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Week #10: (11/9-13) Characteristic Curves, dB & Gain

Post by rjagodowski »

This week we'll finish the A.C. Analysis and A.C. Model of the Common Emitter Amplifier we discussed last week. Here is a link explaining the r-parameter Model of a bipolar junction transistor.

Here's a page on Common Emitter Voltage Divider Bias Summary , pay special attention to the graph showing the sinusoidal variations of iB, iC & VCE. Scroll down about half-way on this page to view the graph. Here's the pic:
Output Characteristic Curves of CE Amplifier.jpeg
Output Characteristic Curves of CE Amplifier.jpeg (96.02 KiB) Viewed 241 times
Our next transistor lab on Common Collector Amplifiers is found here then follow the link to download it from the Registered Users Only area. A printed copy will be given to you in class/lab.

Some summary links:

Here's a good review & practice of Voltage Divider biased transistors from Wisc-online.com . Calculating D.C. Values for a Resistor Bias Class A amplifier, from Wisc-Online.

From this link presented back in Week #8, a summary chart of CE, CC & CB amplifier characteristics was provided. Here it is:
TransistorAmpCharacteristicChart.jpeg (46.07 KiB) Viewed 241 times

PNP Bipolar transistor amplifier: Just for brief example, this link shows the difference between an NPN and a PNP Common Emitter Amplifier, here. Notice the reversed polarity on the power supply. The output of the PNP circuit will be negative with respect to ground.

We'll discuss Gain calculations (below) then continue with the following:

A brief discussion of the power dissipation in a bipolar junction transistor. It is principally due to Vce & Ic. Here is a link to lab post from EET-250L Control System Theory Lab from an experiment most of you will be performing next semester to plot the power dissipation of an NPN transistor. Scroll down to Transistor Plot.

Class A, Class B and Class AB amplifiers, Cross-over Distortion.

We'll spend a bit of time discussing the Output Characteristic Curves (scroll down a bit).

Amplifier Distortion

Here's a link that will let you hear the effects of distortion common waveshapes. http://www.falstad.com/mathphysics.html. Scroll down to the "Signal Processing" simulations, then open the "Fourier Series Applet". These simulation do require a Java-enabled web browser. Set the signal to a sinusoid, set the frequency & volume to a comfortable combination, click the "Sound Option" and listen as you "Clip" the wave. You can also manually distort the wave using your mouse. Note that ANY change (distortion) to the basic sine wave results in higher frequencies being added to the signal. These frequencies are called "Harmonics". An ideal amplifier will amplify the input signal with the least addition of harmonics. Often times you will see a "Total Harmonic Distortion" specification in an amplifier spec sheet. This relates the total amount of distortion which may be added to a signal by that amplifier.

Efficiency, Gain and dBs from AllAboutCircuits.com and Amplifier Gains from Electronic-Tutorials.ws (scroll down a bit).

Decibels, Gain, Power & Voltage from Wisc-online.

A handy summary of dB Conversions.

Amplifier Summary from Electronics-Tutorials.ws.

Wikipedia on Differential Amplifiers, Common & Differential Mode Operation.

Here are some practice problems on Gain Calculations. We'll eventually cover this entire sheet, but for now look at problems 1, 2 & 3. This assignment is also common with the EET-210 Linear class and was discussed in that lecture on 11/4/19.
Gain Calculation Problems v15.1.pdf
(65.29 KiB) Downloaded 33 times

NEXT WEEK'S lecture will begin with a discussion of Junction Field Effect Transistors. Plus review this site before our next class.
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