110 likes | 217 Views
MTRX N410 – I-V Curves for PN Junctions. Richard Summerfield Programme Chair – Engineering Ras Al Khaimah Men’s College. MTRX N410 – I-V Curves for PN Junctions. A diode is an electronic device made from p and n type semiconductor material.
E N D
MTRX N410 – I-V Curves for PN Junctions Richard Summerfield Programme Chair – Engineering Ras Al Khaimah Men’s College R. Summerfield
MTRX N410 – I-V Curves for PN Junctions A diode is an electronic device made from p and n type semiconductor material. The anode is connected to the p type and the cathode to the n type. Anode Cathode Cathode Anode R. Summerfield
MTRX N410 – I-V Curves for PN Junctions The Diode only allows a current to flow through it one direction: - From Anode to Cathode This is known as Forward Bias R. Summerfield
MTRX N410 – I-V Curves for PN Junctions When a diode is Forward biased, it’s anode is connected to a more positive voltage than the cathode. R. Summerfield
MTRX N410 – I-V Curves for PN Junctions When a diode is reverse biased, its cathode is connected to a more positive voltage and it will not conduct. R. Summerfield
MTRX N410 – I-V Curves for PN Junctions An Ideal Diode An ideal diode would act like a conductor when it is forward biased and an insulator when reverse biased. Reverse Biased Forward Biased R. Summerfield
MTRX N410 – I-V Curves for PN Junctions A typical diode has a different I-V curve. It does not conduct until a ‘threshold’ junction voltage is released. A small current will ‘leak’ through in reverse bias. If the reverse voltage is large enough, it will break down. R. Summerfield
MTRX N410 – I-V Curves for PN Junctions Forward Bias The diode will not conduct until the pn junction depletion layer has been overcome. Typically 0.7 volts for Silicon 0.3 volts for Germanium R. Summerfield
MTRX N410 – I-V Curves for PN Junctions Reverse Bias A small current will leak in reverse bias as some electrons will manage to cross the depletion layer due to the effects of thermal energy. If a sufficiently large reverse voltage is applied the diode will breakdown. The breakdown voltage will depend on the diode type. R. Summerfield
MTRX N410 – I-V Curves for PN Junctions Typical I-V Curve for a Diode Note how the scales on the Forward and Reverse Bias areas of the graph are different. The scales used ‘exaggerate’ the curve to show the differences from an ideal diode. R. Summerfield
MTRX N410 – I-V Curves for PN Junctions R. Summerfield