# Problem with mixed CMOS op-amp supply voltages on a square to saw wave converter

I am designing a square wave to saw wave converter by first integrating the square wave into a triangle wave, then toggling between the triangle wave and it's inverse, using 2 CMOS 4066 switches triggered by the original square wave.

The output is an incomplete saw wave because of the triangle wave going too negative relative to the 4066 supply voltage.

I know I could fix this by scaling and adding a DC offset to the triangle waves at the input of each 4066 switch. But for a number of reasons I want to keep the waveforms balanced with no DC offset. I also want to keep the circuit as simple as possible because it will be repeated many times in this project.

Can I power the with 4066 and 4069 with -12v to +12v so as not to cause this problem? If so what is a simple way to shift the logic level of the input to the 4069 to the right level?

• There are FET analog switches that will take +/-15V. Or, run the 4066 off +/-6V and level-shift its control inputs.
– user16324
Commented Sep 13, 2017 at 13:32
• Can I power the with 4066 and 4069 with -12v to +12v Look at their datasheets, for those made by TI it is a no as the maximum supply voltage is 20 V. Why not simply run your circuit from +/- 10 V, then you can supply all the ICs from the same supply lines and avoid the problem you have. For the CMOS logic ICs then a 0 will be -10 V and a 1 will be +10 V. Commented Sep 13, 2017 at 13:49

You can run the 4000 series parts off a bipolar supply but the voltage is limited (IIRC the limit is 20V total which works out to ±10V) and you need to level shift the input signal, this is perfectly doable with a comparator and a few resistors but it's still an extra part.

Or you can use a modern part like the ADG1219. It's a 2:1 mux rather than a plain switch so you don't need an inverter and it has a seperate pin for the logic ground so you can run it off a bipolar supply while controlling it with a unipolar signal.

• I will try reducing the supply voltage. The ADG1219 is a lot more expensive than the 4066. I will am making 180 of these circuits for a polyphonic synthesizer. Commented Sep 13, 2017 at 16:14