## PNP Transistor Common Base question

 In a PNP common base configuration circuit, how about if the circuit is set up at reverse configuration. Say no voltage source at emitter pin and just passive load. At collector pin there is voltage supplied. There would be base current at the base pin but will it be current flowing from collector to emitter? by manuelkw January 12, 2018 Sounds like zero-zero if I understand you correctly. Can you give actual voltages wrt base? by mikerogerswsm January 12, 2018 A bias resistor at base pin is 5K to GND, voltage supplied at C pin is 3V by manuelkw January 12, 2018 Sorry, I don't understand. Can you post full schematic surrounding that device? by mikerogerswsm January 13, 2018 The circuit looks like this : https://drive.google.com/open?id=1fV9PW6cXwjCE3ILMMEdMmIMQfujKlu5P Definitely CB has current but I found current flowing at the emitter to the load resistor, not understand why. by manuelkw January 13, 2018 From the picture, the bias conditions are following: VE = 0V VB = 0V VC = 3V Hence, you should observe no currents. by coolman January 15, 2018

 If you connect your PNP 'backwards' with reversed polarity, it looks roughly like two diodes, but not quite. You have biased the collector-base diode 'on', which puts the base at + 2.4 volts, with a current of 480 uA. The emitter-base diode is reverse-biased, and, were it just a diode, would pass no current. But there are a lot of carriers floating around and I suspect some are finding their way to the emitter. PNPs are not intended to work backwards. I suggest adding a diode in series with the emitter (or base) to block this effect. +2 votes by mikerogerswsm January 13, 2018 PS - There may also be an emitter-collector diode inside the chip which is normally reverse-biased and which you are turning 'on'. You need to look at the chip structure, is it a vertical or a lateral PNP? by mikerogerswsm January 13, 2018 This may be relevant: http://www.joerg-berkner.de/Fachartikel/pdf/1999_ICCAP_UM_Berkner_Modeling_VPNP_using_Vbic.pdf . I'm just a dull old retired engineer and can't pretend to understand it. by mikerogerswsm January 13, 2018

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