PWM generation using Arduino uno
You can't squeeze 100kHz out of an Arduino without a major software rewrite (at which point you will be using an AtMega chip rather than Arduino). analogWrite defaults to ~500Hz and can be boosted to 62.5kHz on some Arduino models, and only for 2 pins. Other PWM pins are capped at 31.4kHz.

You can achieve 100kHz PWM by toggling pins manually and busy-waiting, but you won't be able to do anything else during this. Or you can make use of interrupts, which is a big leap from Arduino ecosystem as I already said.