@K0DPW, You may find it helpful to read the Simulation Tutorial, (3) in (2) in: [https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a](https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a)<br> <br> before attempting simulations in EasyEDA. There is currently no spice model for the CD4027 JK flip-flop available in EasyEDA. There are a couple of options as to what you can do next. 1. Change your design to use the 74HC112 or one of the other 74HC series JK flip flops: 74HC73/107/109 for which there are models available;  2. Request that a CD4027 model to be developed and added to the library for EasyEDA. There is normally a fee for this service. For this option please contact me at _[my_username]@easyeda.com_.

Thanks for the reply. My application ultimately requires a positive edge triggered chip, 74HC109 seems to be the only one of the 74HC family that is positive edge triggered, although I suppose I could input an inverted clock signal. The transition times of the 74HC family also seem to be orders of magnitude faster than the CD4027, which is better for my application anyhow. I'll play with 74HC109 and see how it goes.

Don't forget that the supply voltage for the 74HC series only extends to about 6V, not the 15V or so of 4K series. :)