lesson #3 transistor biasing for designing amps part 2

continuation from last blog.

Here are the actual pics on my oscilloscope (usb scope) the green is the output waveform. My real (breadboarded) circuit did better than the simulation.

The original amp with no bypass cap put in there across the 1.6K ohm resistor for Q2 emitter.

1572203593546.png


1572203600550.png


1572203608384.png


Now with the bypass cap inserted, on the Q2 emitter resistor.

First just as simulated with the ~= 240mV input I was getting the distorted neg. clipping, just as the simulator showed.

1572203617161.png

1572203623585.png




Then reducing the input down to around 160mV pk-pk, the sinewave was non distorted, at around 885mV pk-pk.

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I had to use my analog scope as the input voltages were getting too small for my USB scope to handle properly

Now the results of adding the pre amp CE stage.

1572203645234.png






.
Here is the breadboard layout, you'll see a couple of filter capacitors on the board to get rid of some noise showing up on the scope.
I always put a 0.1uf cap from ground to the input capacitor on the driver side, to filter Rf noise in the amp. I also included a emitter bypass cap, across the emitter resistor of the preamp as well, it gave some improvement, not really needed.

1572203654497.png


This should get you started in the direction of biasing transistors for any reasonable value of current or voltage output, required for each application.

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