Working of a transistor (pnp)
• Consider a pnp transistor operated in active region as shown in Figure.
• Since the EB junction is forward biased large number of holes present in the emitter as majority carriers are repelled by the +ve potential of the supply voltage VEB and they move towards the base region causing emitter current IE.
• Since the base is thin and lightly doped very few of the holes coming from the emitter recombine with the electrons causing base current IB and all the remaining holes move towards the collector. Since the CB junction is reverse biased all the holes are immediately attracted by the –ve potential of the supply VCB. Thereby giving rise to collector current IC.
• Thus we see that IE = IB + IC -----------------(1) (By KVL)
• Since the CB junction is reverse biased a small minority carrier current ICO flows from base to collector.
• Consider a pnp transistor operated in active region as shown in Figure.• Since the EB junction is forward biased large number of holes present in the emitter as majority carriers are repelled by the +ve potential of the supply voltage VEB and they move towards the base region causing emitter current IE.
• Since the base is thin and lightly doped very few of the holes coming from the emitter recombine with the electrons causing base current IB and all the remaining holes move towards the collector. Since the CB junction is reverse biased all the holes are immediately attracted by the –ve potential of the supply VCB. Thereby giving rise to collector current IC.
• Thus we see that IE = IB + IC -----------------(1) (By KVL)
• Since the CB junction is reverse biased a small minority carrier current ICO flows from base to collector.
