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Electronics Handbook/Circuits/NPN Transistor Configurations/Amplifier with 4 Resistors

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Configuration

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Analysis

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Assume that the transistor is ideal.


When or R1 = 0. The equation above is reduced to

R3 = 0 ,
R3 = R4 ,
R3 = 2R4 ,
R3 = (n+1)4 ,


When . The equation above is reduced to

When R1 = 0 or R2 = 0,

. Transistor operates like a closed switch

When R2 >> R1

. Transistor operates like an opened switch

With the right biased voltage at the base, the transistor can be operated like a mechanical switch.