Hi All
I'm busy building a function generator using a XR2206 IC, I've downloaded the datasheet for it and a couple circuits off the net and used them to compile my schematic.
However there are a couple areas I would appreciate some help on.
1 - Is the use of the 5k POT connected to SV5 correct, I found it on a circuit off the web stating it would set the offset?, but it doesn't illustrate this in the datasheet, but rather a voltage diver using 2 x 5.1k resistors between +12V and 0V.
2 - Pin9 must have an internal pullup resister, as if left open it defaults to its "high" logic function. To change the function you need to pull it low, so the FSK Sw con would work fine, however, if an external trigger is used, what if the input voltage exceeds 5V? Do I need to use a Zener diode to protect against overvoltage?
3 - As the XR2206 can produce a sawtooth wave if the FSK (pin9) is connected to the sync output, so I've wired it up through the rotary swich so that if its turn to the sawtooth position, it will then do so, and in such a way that one could not sort the sync output to ground if the FSK switch is closed. I've added diodes (D1, D2) to the FSK connection, to prevent any applied voltage (say from a 555) to the EXT FSK trigger from being shorted if the FSK Switch is closed. Is this correct? hope that makes sense!
4 - I'm wanting an offset function (if point 1 indeed doesn't work), would it be best to use an output buffer opamp on the outputs and one could incorporate the offset into this?
5 - Are there any other recommendations that would make this circuit better.
Thanks in advance!