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I know [itex]G_P (dB) = 10log(G_P)[/itex] and [itex]G_V (dB) = 20log(G_V)[/itex] and [itex]G_I (dB) = 20log(G_I)[/itex].

I also know that [itex]G_P (dB) = G_V (dB) + G_I (dB)[/itex].

So, if I have a common base amplifier whose current gain is [itex]G_I (dB) = 0[/itex], then [itex]G_P (dB) = G_V(dB)[/itex].

Suppose

[itex]G_V (dB) = 20 dB[/itex]. So [itex]G_V = 10^{20/20} = 10[/itex]

[itex]G_I (dB) = 0 dB[/itex]. So [itex]G_I = 10^{0/20} = 1[/itex]

As I've written above, then [itex]G_P (dB)= G_V (dB) = 20 dB[/itex]. So [itex]G_P = 10^{20/10} = 100[/itex].

But, in linear scale (not in dB), [itex]G_P = G_V\cdot G_I[/itex], so [itex]G_P = 10\cdot 1 = 10[/itex], which is not [itex]100[/itex].

What's wrong?

Thanks!