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help in understanding this circuit.

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s3034585

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hi

can some one pls explain use of diode in the about circuit across the bjts.


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sau_sol

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the diodes are used for the protection of the transistors
so the voltage will always be in the intended direction and if the voltage polarity reversed it will protect the circuit
 

deepuj

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D2 and D4 are there to keep a constant bias voltage at the transistor bases...

And I am sure that D3 is not for any polarity reversal protection...!
 

salvaber

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The connector belogs to A rs562 562 connection that means the voltage in the wires can be negative. D2 and D4 have the pourpose of clamping the negative part of the signal.
D1 is connected to a reset circuit that is generated discharging C20 while pushing S1. If the 3.3V power supply drops, che capacitor C20 discharges through D1 generating reset
 

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