D
Dave
Trying to hook up a 7805 +5V regulator as well as a 7905 -5V regulator to my
circuit, thus providing the +/- voltages for the 74HC4053 triple 1 of 2
multiplexor. Problem is, I'm not sure how to do this. The 7805 has its
three pins labeled in the datasheet (from left to right)
input/ground/output, and I'm assuming that the input is +voltage, ground is
negative, and the output is the advertised +5V. This at least makes sense
to me.
The 7905 is another matter. From left to right its pins are labeled (in the
datasheet) GND/input/output. Assuming (hate that word) that it's input is a
negative voltage (because it's output is negative) that makes the GND a
positive voltage. Can that be right? Or do I make GND negative, and the
input positive? Somebody please help with this. One person told me that
the 7905 can have an input of either positive or negative, which would lead
to the ground being interchanbably positive or negative. That doesn't sound
right, but I've been wrong before. One thing seems obvious- I cannot have a
negative ground for my 7805 and a positive ground for my 7905. This, it
seems, would fry my 74HC4053. (Back to the negative ground and positive
input for a -5V output...) What to do?
Ignorantly yours,
Dave
circuit, thus providing the +/- voltages for the 74HC4053 triple 1 of 2
multiplexor. Problem is, I'm not sure how to do this. The 7805 has its
three pins labeled in the datasheet (from left to right)
input/ground/output, and I'm assuming that the input is +voltage, ground is
negative, and the output is the advertised +5V. This at least makes sense
to me.
The 7905 is another matter. From left to right its pins are labeled (in the
datasheet) GND/input/output. Assuming (hate that word) that it's input is a
negative voltage (because it's output is negative) that makes the GND a
positive voltage. Can that be right? Or do I make GND negative, and the
input positive? Somebody please help with this. One person told me that
the 7905 can have an input of either positive or negative, which would lead
to the ground being interchanbably positive or negative. That doesn't sound
right, but I've been wrong before. One thing seems obvious- I cannot have a
negative ground for my 7805 and a positive ground for my 7905. This, it
seems, would fry my 74HC4053. (Back to the negative ground and positive
input for a -5V output...) What to do?
Ignorantly yours,
Dave
