P
pawihte
I want to use a classic 555 timer IC to drive the base of a PNP
transistor through a resistor, the emitter of the transistor
being tied to the 555's Vcc. The 555 datasheet gives a graph for
the high-state output voltage vs. sourcing current, but not when
the load is tied to Vcc.
Vcc
--------------------------
| |
.|. |
| | |
| | |
'-' |
| |
555 out ___ | |<
------------|___|------|
|\
|
|
What I'm concerned about is: Is there a possibility that the
high-state output of the 555 drops low enough below Vcc to
partially turn on the PNP transistor? I could increase the
turn-on threshold of the transistor with diodes, an LED or a
resistive voltage divider, but I'd like to avoid that if it's not
needed.
transistor through a resistor, the emitter of the transistor
being tied to the 555's Vcc. The 555 datasheet gives a graph for
the high-state output voltage vs. sourcing current, but not when
the load is tied to Vcc.
Vcc
--------------------------
| |
.|. |
| | |
| | |
'-' |
| |
555 out ___ | |<
------------|___|------|
|\
|
|
What I'm concerned about is: Is there a possibility that the
high-state output of the 555 drops low enough below Vcc to
partially turn on the PNP transistor? I could increase the
turn-on threshold of the transistor with diodes, an LED or a
resistive voltage divider, but I'd like to avoid that if it's not
needed.