We have been asked to create a Ramp(sawtooth) Wave out of Square wave by using PMOS, NMOS, Capacitor and a Square Waveform. I tried a couple of configuration in LTSpice but to no avail. The hint says capacitor charges linearly but I then how does the voltage go to 0 in a matter of few ns?

 

Are you supposed to design the circuit using the elements such as found in a CMOS IC process?

 

Are you sure you aren't supposed to create a triangle-wave rather than a saw-tooth from the square-wave? For that the voltage doesn't have to go to 0V in a short time.

 

Shouldn't this be in the 'Homework Help' forum?
Who says the voltage has to go to 0V?
Consider how you will get the cap to charge linearly, and how you will establish a threshold voltage at which you should start to discharge it.

 

It turns out we have to use the CMOS and make an inverter, but then as said by crustchow, I am getting a saw-tooth wave and it has much less voltage amplitude than the pulsating wave. I changed the capacitor value to 1nF and pulsating wave duty cycle to 90% and got much ramp-like wave. Thanks.

 

It turns out we have to use the CMOS and make an inverter, but then as said by crustchow, I am getting a saw-tooth wave and it has much less voltage amplitude than the pulsating wave. I changed the capacitor value to 1nF and pulsating wave duty cycle to 90% and got much ramp-like wave. Thanks.

So now I want to hear how you propose to build a 1nF capacitor using your CMOS process