Hi!
I am doing an embedded design project and need some help with the following please.
I have an on switch (push n/o) that when pushed applies Vcc to the micro and switches on. With code I then have a pin pulled high, fed to a pnp transistor to keep the micro on when the switch is released. See attached schematic.
I have done some calculations with Ib = 15mA (hard on current) and found the values as shown in the schematic. Rb = 227ohm and Re = 2.7ohm. But when I simulate it (circiutmaker), I get a value of 8,xV where I want the 4,5V. For my calculations I also used a beta of 10 (Ic/Ib as found on the data sheet).
Are my calculations wrong, or where am I going wrong?
Thanks
I am doing an embedded design project and need some help with the following please.
I have an on switch (push n/o) that when pushed applies Vcc to the micro and switches on. With code I then have a pin pulled high, fed to a pnp transistor to keep the micro on when the switch is released. See attached schematic.
I have done some calculations with Ib = 15mA (hard on current) and found the values as shown in the schematic. Rb = 227ohm and Re = 2.7ohm. But when I simulate it (circiutmaker), I get a value of 8,xV where I want the 4,5V. For my calculations I also used a beta of 10 (Ic/Ib as found on the data sheet).
Are my calculations wrong, or where am I going wrong?
Thanks
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