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
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
Also you do not need a 50mA base drive current to saturate a BC547 with an Ic=100mA.
It has an hFE of at least 100 at 100ma, so I would use a base drive of say 5mA max.
So, from 3.3V, allowing a Vbe of 0.7V = 2.6v/0.005 = 520R... pref value say of 470R.
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.
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.
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.
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.??
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.??
oh ! I think he wants to control lcd backlight ! but he doesn't understanding to use lcd.....
I think if he wants to control lcd it's all depented on code in MCU.. to on/off lcd... and the current supply for Backlingt that can be controlled by a resistor variable..
eric,
your circuit is right but. i need just a wire coming out from the collector.
shall i replace the load in ur figure with some resistor and take a o/p wire from the collecor ....