hi everyone
I have a circuit with a 4047 logic chip used as clock source (range 20Hz to 100Hz), and I need drive a chip whose inputs cannot be more than about +9V.
Since the 4047 is powered using +15V, its outputs would be 0/+15V if I’m not wrong.
How can I shift them down to 9V?
a simple voltage divider is enough? Or do you think I could use some hex buffers powered using +9V (so I would also buffer the clock).
Alternatives?
The “classic” answer is to use an open collector buffer that can accept the 15V input and pull up the output to 9V. However, if you don’t need the speed, you can just clamp the 4047 output with a resistor and a 9V zener.
thank you,
the classic way would be perfect,
but how can I implement that? using a transistor? or an opamp?
btw, in my first post I did a mistake, the clock speed is actually 20KHz to 100KHz, not 20Hz
See figure 4 in [this page. The example uses a totem pole buffer which is simpler than an open collector one.](http://digital.ni.com/public.nsf/allkb/826C981B3D0D3A9786256DD300188620)