We learn here a Single Stage Common Emitter Amplifier. The upper part is the amplifier circuit and the lower part shows the BJT transistor characteristic output curves and the amplifier's input and output waveforms.

The green line in the chracteristic curve is the amplifier's static load line (or DC load line). The gray dot on the DC load line is the amplifier's DC operating point. In this applet, we can see, given an input waveform, the corresponding output waveform. Every input point has a corresponding output point and they should be always on the DC load line.

Users can have an overview of how the amplifier works and using mouse, can drag and change several parameters and see what happens to  the amplifier. The user can use the mouse to control the lower part of the applet, i.e. the characteristic curve's part, and the amplifier's parameters will change accordingly. The new parameters show up in the upper part of the applet, i.e. the circuit part of the amplifier.

[1]. Change the Amplitude:  Point mouse on the upper boundary or lower boundary of the input waveform yellow area and drag the mouse to change the waveform's amplitude, after the mouse is released we can see the new waveforms on the applet.

[2]. Change the Vcc Value: Point mouse over the x-intercept of the DC load line and drag it.   See the corresponding change in the Vcc value ?  In the mean time, we can see the new Vcc value in the circuit part.

[3]. Change the Rc Value: Point mouse over the cross point  the y-intercept of the DC load line and drag it.  See the corresponding change in the Rc value ?   In the mean time, we can see the new Rc value in the circuit part.

[4]. Change the operating point : Point mouse on the gray dot in the DC load line and drag it.   See the corresponding change in the operating point ?

Notice: when the user is going to change the amplifier's parameters out of their correct ranges, the applet will warn the user. For example, soppose we want to change the operating point of the amplifier and we can drag the gray dot on the DC load line to see the corresponding change of the input and output waveforms. But we can not set the operating point too small, otherwise we will enter the sutaration region of the BJT transistor. Hense the output waveform's lower bound (left side) will be distorted and in such a case the applet will show you the minimum lower bond using dashed red line and warns the user. And the applet doesn't allow the user to change the operating point smaller. On the other hand, we can not change the operating point too large, otherwise, the output waveform's upper bond (right side) will greater than Vcc and will be distorted. The same thing will happen when we are trying to change the other parameters, such as the input waveform's amplitude, Vcc and Rc value.