Hey All,
I am trying to finish up on a Christmas project and I need some one to verify my transistor math. My goal is to determine if the NPN Transistor 2N2222A is correct and the appropriate base resistor. Here are the specs:
-Shift Register: DIP-16, SN74HC595NE4, Spec Sheet, Input Voltage 5v, Max Ic Current (of one pin) 20mA(?)
-NPN Transistor: 2N2222A, Spec Sheet, Ic max = 800mA, hFE specs:
hFE (Ic = 10mA, Vce 10v) = 75
hFE (Ic = 150mA, Vce 10v) = 100
hFE (Ic = 500mA, Vce 10v) = 40
-Red LED; Foward Voltage = 2v, Foward current = 30mA with a 150 ohm resistor.
Here is the schmatic:
Here is my math (formulas used from this site):
Is this correct a 3.75 ohm base resistor?
I am trying to finish up on a Christmas project and I need some one to verify my transistor math. My goal is to determine if the NPN Transistor 2N2222A is correct and the appropriate base resistor. Here are the specs:
-Shift Register: DIP-16, SN74HC595NE4, Spec Sheet, Input Voltage 5v, Max Ic Current (of one pin) 20mA(?)
-NPN Transistor: 2N2222A, Spec Sheet, Ic max = 800mA, hFE specs:
hFE (Ic = 10mA, Vce 10v) = 75
hFE (Ic = 150mA, Vce 10v) = 100
hFE (Ic = 500mA, Vce 10v) = 40
-Red LED; Foward Voltage = 2v, Foward current = 30mA with a 150 ohm resistor.
Here is the schmatic:
Here is my math (formulas used from this site):
Rich (BB code):
load current Ic = supply voltage Vs
load resistance RL
hFE(min) > 5 × load current Ic
max. IC current
Rb = Vc × hFE where Vc = IC supply voltage
5 × Ic (in a simple circuit with one supply this is Vs)
_______________________________________________________
.02 A or 20mA Ic = 12Vs
600 Ohm R L
(note: 150 * 4 = 600)
hFE(min) > 5 × 20mA__
20mA
75(min) > 5
RB = 5Vc × 75
5 × 20mA
where Vc = IC supply voltage
(in a simple circuit with one supply this is Vs)
RB = 3.75 ohm