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Current and Voltage Limits

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skill34

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Can anyone help me with this problem?:

What is the minimum value of R in the circuit(description is forthcoming) if the maximum op amp output curent is 5mA and the current gain of the transistor is βf>50?

Circuit Description:

Inverting op amp in series with npn transistor who is in parallel with a resistor "R".

collector voltage=+25V
 

Are you sure the circuit is drawn correctly?

doesn't match ur description.
 

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    skill34

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If you use lets say 40 ohm res then:
10V/40 ohm= 0.25A (Ibmax=5mA then Ie=5mA*50=0.25A)
power Dissipation on Q will be 0.25A*15V=3.75W
 

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    skill34

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