Here is a demonstration of how one can perform real time simulation of BJT amplifier using Proteus software and PC Soundcard. Real time here means the BJT amplifier circuit designed in Proteus is put to test with real signal from PC microphone input in real time. This allows us to test and study the designed amplifier with real input signal. The real input signal can be audio or sine wave, square wave signal or any other type of signal from a waveform generator. Here the designed BJT amplifier is fed with sine wave signal using a microphone component. The microphone component receives signal from the PC microphone input. We can use signal generator source such as from a mobile phone device or PC oscilloscope and plug it the soundcard microphone/line in port of the PC where the proteus software is running.
The following is quick video demonstration of how this work.
Here we will test the BJT amplifier designed in our earlier tutorial How to bias a BJT using voltage divider biasing. The resistor and capacitors were calculated in that tutorial and the circuit implementation in proteus is shown below.
The microphone component MIC in the above proteus schematic receives real signal from waveform generator. Here we will use a free software soundcard scope to generate a sine wave on the PC speaker. You can download soundcard scope software from the following link:
https://www.zeitnitz.eu/scms/scope_en?mid=4.01
The output of the PC speaker is connected back into the microphone/line in port of the PC using a male to male 3.5mm audio jack. The microphone labelled MIC in the above circuit will read into proteus simulation circuit the sine wave sent by soundcard scope software from the speaker port.
First of all you should connect the male to male 3.5mm audio jack to the speaker and the mic/line in port of your PC(where proteus software is running). See picture below which connects speaker output into line in or mic port input.
When you insert the jack into the mic/line in port you might get "which device did you plugin?" in windows OS. Select Line In.
Then you should open the soundcard scope software and select the signal generator tab. There in the channel 1 option choose sine wave, enter 0.01 in the amplitude field for 10mV amplitude and enter 1000 in the frequency field for 1KHz frequency. And finally press the channel 1 button to enable the output. This is as shown in the figure below.
Now in the proteus software we will setup the oscilloscope to view the signal coming from the PC speaker and also the amplifier output signal.
Now if we run the simulation we can view the amplifier input and output signal on the proteus oscilloscope. Note that it takes a 1 second or so for the signal to appear because the data is buffered a bit before display. The following shows real time signal display using proteus oscilloscope.
These signals are updated in real time. The yellow signal is the signal from the soundcard scope software generated signal which is the input the designed BJT amplifier and the blue is the amplified signal due to the amplifier. We can change the frequency and amplitude of the input signal from the signal generator and see live update of the input and amplified signal on the proteus oscilloscope. This has the advantage to test designed circuit live from the simulation software before building the circuit. It has the advantage of saving time and confirm that the designed circuit works as expected. We can not only test BJT amplifier but also any other circuits.
The next step would be to actually build the BJT circuit. The tutorial How to Build BJT amplifier and test with Soundcard based PC Oscilloscope illustrates this. The above BJT amplifier circuit is build on a breadboard and test with real signal in real time.
You might also be interested in the following tutorials:
- How to build base biased BJT amplifier on breadboard and test with PC soundcard based oscilloscope
- Testing of self biased BJT amplifier on breadboard with PC oscilloscope
- Construction of Collector-Emitter Feedback Bias BJT Amplifier Test with PC Oscilloscope
