In a pnpn diode 2 junctions r FB n the middle one is RB under forward blocking conditions....the anode-cathode current is very small since the current cannot pass through the RB n-p junction in the middle...On the other hand in a BJT acting in the linear region the B-E junction is forward biased but the C-B junction is RB,but current seems to flow pretty smoothly through the device....So why does this RB junction discriminate against the current only in the pnpn diode n not the BJT?????