ADALM2000 Activity: The BJT Connected as a Diode : PNP Section

When following the circuit diagram and directions above, the output waveform generated the image shown in figure 1.  This is at 100 Hz with the waveform being flipped compared to the answer (figure 7 on the website).  When changing the input frequency to 1kHz, it becomes the waveform in Figure 2.  Why is the waveform in figure 2 flipped compared to the answer of figure 7 and what do the waveform represent in figure 7?  Also, why does current conduct (at R1) when VBE goes negative?

Figure 1

Figure 2



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[edited by: 200505408 at 6:47 PM (GMT 0) on 26 Jul 2020]
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  • Hello,

    It seems that you haven't connected/turned on the negative power supply (Vn = -5V).

    It should work the same for 100Hz / 1KHz.

    Without Supply:

    With Supply:

    This experiment, as stated in the objective, investigates the reverse break down voltage. With this signal we cover the entire breakdown voltage range that is supported by the PNP transistor (2n3906) stated in the datasheet VBR=5V.

    Regards,

    Antoniu

Reply
  • Hello,

    It seems that you haven't connected/turned on the negative power supply (Vn = -5V).

    It should work the same for 100Hz / 1KHz.

    Without Supply:

    With Supply:

    This experiment, as stated in the objective, investigates the reverse break down voltage. With this signal we cover the entire breakdown voltage range that is supported by the PNP transistor (2n3906) stated in the datasheet VBR=5V.

    Regards,

    Antoniu

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