T circuit represents a tactile sensor to turn on / off a relay to turn on / off a load of greater power.The tactile sensor consists of two separated metallic contacts about 2mm.When you place your finger on one of these contacts circulates certain current between them.
hFE (T1) = 300 hFE (T2) = 220 Vgama VCEsat = 0.7 V = 0.5 C
Considering that the relay needs a current of 70 mA to close the contacts and that in this case both transistors should be saturated.Determine
1)hFE min for transistor T2
2)The minimum current that should flow in the tactile sensor when ativated(that is pressed by the finger)
1)How can i determine the mininum hfe of T2.The hFE of T2 must a have so that we have Ic2 sat =70 mA
I have tried to do \( 12 V=Vcesat1+1kOhm*(Ic1sat)+VBE2 sat
12 V=0.5 V+1kOhm*(70 mA)+VBE2sat \)
but i am not going nowhere form here.
Where should i start for determing this?
Thanks
hFE (T1) = 300 hFE (T2) = 220 Vgama VCEsat = 0.7 V = 0.5 C
Considering that the relay needs a current of 70 mA to close the contacts and that in this case both transistors should be saturated.Determine
1)hFE min for transistor T2
2)The minimum current that should flow in the tactile sensor when ativated(that is pressed by the finger)
1)How can i determine the mininum hfe of T2.The hFE of T2 must a have so that we have Ic2 sat =70 mA
I have tried to do \( 12 V=Vcesat1+1kOhm*(Ic1sat)+VBE2 sat
12 V=0.5 V+1kOhm*(70 mA)+VBE2sat \)
but i am not going nowhere form here.
Where should i start for determing this?
Thanks
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