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hi all,
i am having bc 547 npn transistor,
i need it to act as a switch.
supply voltage is 3.3 volts.
please guide me in designing the circuit(like rb rc values etc)
i need to drive 300milli amp.
input will be 50 milli amp
even if it drives 100ma ,its enough.
my requirement is a 50 ma i/p should drive 100 m/a o/p device with a supply voltage of 3.3 volts
i need to drive 300milli amp.
input will be 50 milli amp
eric
in my board i have only a 3.3v supply with 50ma .... with this i need to drive
a component of 3.3v 100ma ....
please say me how to calculate rb and rc.
i am not going to connect the load across vcc and collector of transistor.
So i need to put a resistor (Rc) instead of connecting load.
hope u get it..
ya,
but an transistor can do this current amplification know.
that 3.3 v 50 ma is from my micro controller .
and 3.3 v 100 ma is LCD .
i need to turn ON and OFF the LCD by my code.
But my micro controller cant directly do that because of low current rating.
that s why i go for a transistor switch.
hi,
I dont understand what you mean by that 3.3 v 50 ma is from my micro controller are you talking of the MCU pin output current rating.?
If so use a 470R from the MCU pin to drive the base of a transistor.
When you say switch the LCD on/off do you mean the lcd backlight or the actual lcd display.??
EDIT:
i need the LCD to get completely switched off ,both backlight and display.
backlights drive around 200ma.
the lcd in my circuit wastes power.
so i need the lcd to get turned on only when i need
i am using an nokia 6100 . just now i checked data sheet.
the lcd backlight uses 5o ma.