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While observing the input characteristics of a Bipolar Junction Transistor(BC547), I observed from the graph that the reverse voltage gain came out to be negative. Is this possible and if so, what is it's physical significance? If not, is this observation simply due to the non-ideality of conditions of the experiment or just some error?

schematic

simulate this circuit – Schematic created using CircuitLab

Note that both sources shown in schematic are not actually just 30V, they can be varied from 0 upto 30 V.

Updated the schematic. Note that I am plotting graph of VBE vs IB with VCE constant for input characteristics and graph of VCE vs IC with IB constant for output characteristics.

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    \$\begingroup\$ Since forward gain in common emitter configuration is negative, it's possible. Add the schematic to the question to get a definite answer. \$\endgroup\$
    – user16324
    Commented Sep 26, 2017 at 18:36
  • \$\begingroup\$ @BrianDrummond Updated the question, check it now. \$\endgroup\$
    – akshayk07
    Commented Sep 27, 2017 at 14:27
  • \$\begingroup\$ @SpehroPefhany Updated the question. \$\endgroup\$
    – akshayk07
    Commented Sep 27, 2017 at 14:27
  • \$\begingroup\$ Vc decreasing as Vbe increases is correct for that circuit configuration \$\endgroup\$
    – sstobbe
    Commented Sep 27, 2017 at 20:25

2 Answers 2

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Edited now that meaning is clear:

I don't think you should see a negative DC reverse gain in this configuration. You could have some kind of EMI pickup if this is an experimental (as opposed to simulation) measurement.

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  • \$\begingroup\$ So, are you suggesting that I might have connected the emitter as the collector and vice versa? Because I got reverse voltage gain as -0.02 which is a small negative number. \$\endgroup\$
    – akshayk07
    Commented Sep 27, 2017 at 14:38
  • \$\begingroup\$ I thought reverse voltage gain meant 1/forward voltage gain i.e. input voltage / output voltage. As in one of the hybrid parameters. \$\endgroup\$
    – akshayk07
    Commented Sep 27, 2017 at 16:38
  • \$\begingroup\$ @akshayk07 Yes, we need clarification. The schematic does not show where the input and output voltages are measured. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Sep 27, 2017 at 17:50
  • \$\begingroup\$ Updated the question. \$\endgroup\$
    – akshayk07
    Commented Sep 27, 2017 at 18:11
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Yes, is negative, vbe voltage drops in active region

https://www.eevblog.com/forum/projects/why-transistor-vbe-drops-when-transistor-is-in-active-region-bc547-ibconstant/msg5458733/#msg5458733

I don´t know why, I think that´s hre, h12

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