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Electronics Handbook/Circuits/NPN Transistor Configurations/Amplifier with 4 Resistors
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Configuration
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Analysis
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.