bjt current mirror configurations

bjt current mirror configurations - #1 ( Current mirror...

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#1 ( Current mirror – basic): ( 29 ( 29 REF O REF O REF O O C C C B C B2 B1 C1 B C1 REF C C2 C1 B B2 B1 C2 C1 B2 B1 BE2 BE1 T BE S B T BE S C 2 1 I I 1 I I 1 β If, β 2 1 I I Thus, β 2 1 I β 2 1 I β I 2 I 2I I I I I ' I I I I I I and I I I i i i i V V Noticed, V v exp β I i V v exp I i β β Given, + = + = + = + = + = + + = + = = = = = = = = = = = Page 1 of 9
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Question #2: The I C2 can be decreased, equaled to or increased with comparing with the I C1 by changing the ratio of the transistor emitter areas and changing the ratio of the emitter resistor accordingly. Key point: * V B for Q1 and Q2 must be equal Test condition #1: I C2 = 2 1 I C1 Q2 = 2 1 Q1 (half the area internally) and R 2 = 2R 1 ( 29 [ ] ( 29 REF C1 C1 E1 E1 C1 E2 E1 E1 C1 E2 C1 S1 S1 C1 T E1 C1 E2 C2 C1 S1 S2 C2 T E1 C1 E2 C2 I 2 1 I 2 1 I 2R R I R R 0 R I R 1 I I I 2 1 I 2 1 ln αV R I R 1 I I I I I ln αV R I R 1 I = = = - = - = - = Page 2 of 9
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Test condition #2: I C2 = I C1 Q2 = Q1 (same area) and R 2 = R 1 ( 29 ( 29 ( 29 { } REF C1 C1 E2 E1 E1 C1 E2 C1 C1 T E1 C1 E2 C1 C2 T E1 C1 E2 C2 E2 C2 E1 C1 C1 C2 T E2 E2 E1 E1 S C1 T S C2 T RE2 RE1 BE1 BE2 RE2 BE2 RE1 BE1 I I I R R 0 R I R 1 I
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bjt current mirror configurations - #1 ( Current mirror...

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