Question about the BJT as switch circuit

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    Bjt Circuit Switch
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SUMMARY

The discussion focuses on designing a circuit to control four BJTs (Bipolar Junction Transistors) as switches. The user successfully controlled one BJT but encountered issues when attempting to control two BJTs simultaneously, regardless of the resistance values used. The problem was identified as potentially stemming from the bases being supplied with a negative voltage in the second diagram presented.

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Electronics students, hobbyists designing transistor circuits, and engineers working on circuit control systems will benefit from this discussion.

shinsj
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1. Homework Statement
my teacher wants me to design a circuit to control the on or off of 4 BJTs in the circuit.


Homework Equations





The Attempt at a Solution


so i tryed to control a BJT at once .. it workshttp://user.qzone.qq.com/259234914/infocenter#!app=4

but there were somewrong with control 2 bjt in the circuit .. the BJT can not work whatever i put the value of resistance in the circuit .http://user.qzone.qq.com/259234914/infocenter#!app=4
 

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In the second diagram, the bases appear to be supplied from a negative voltage.
 

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