3-Handouts_Handout_3b - Check for saturation is β forced...

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DC Analysis 1. Start with the E-B junction loop, if the junction is reverse biased the transistor is either cut-off or inverse active (most likely cut-off) 2. If the E-B junction is forward biased assume its voltage drop = 0.7V and using KVL calculate I B (or I E ), you may need to use Thevenin’s theorem to reduce the circuit. 3. Assume the transistor to be active and calculate I C from the relation I C = β I B (or I C = α I E ), you may need to use this formula in step 2 4. From the output loop and using KVL calculate V CE for NPN (or V EC for PNP) 5. Check for your assumption by comparing V CE to V CEsat 0.2V for NPN (or V EC to V ECsat 0.2V for PNP) 6. If your assumption is invalid the transistor will be in saturation, repeat by assuming V CE =V CEsat (Don’t assume any currents) 7.
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Unformatted text preview: Check for saturation is β forced =I Csat /I B < β DC Analysis Examples Calculate the transistor operating point (I c , V CE ) in the following circuits assuming β =100, V BE = 0.7V and V CEsat = 0.2 V. What is the region of operation? I C = 0.99 m.A V CE = 2 V Active I C = 0.96 m.A V CE = 0.2 V Saturation I C = 0 m.A V CE = 10 V Cut-Off DC Analysis Examples (cont.) I C = 4.6 m.A V EC = 6.1 V Active I C = 4.3 m.A V CE = 1.4 V Active I C = 0.86 m.A V EC = 0.2 V Saturation DC Analysis Examples Calculate the current in all branches and the voltage of all nodes in the following circuits assuming β =100, V BE = 0.7V and V CEsat = 0.2 V. What is the region of operation? Active DC Analysis Examples (cont.)...
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This note was uploaded on 01/16/2010 for the course EE ee203 taught by Professor Electronics1 during the Spring '09 term at King Fahd University of Petroleum & Minerals.

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3-Handouts_Handout_3b - Check for saturation is β forced...

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