Re: Schmmit Triger
this is simply as follows.when the output (read voltage level at node "OUT")state is 1 and input is at zero.now,when output is logic one the source of tran M3 will be at Vdd-Vth3.now when the input is increased to Vth1,tran M1 turns on,this will start bringing the potential of source of M3 towards ground.so when the input becomes Vth2+Vsource(M3),then this is the switching point of the schmitt trigger,this is one switching point ,the other can be solved in the same manner ,for the pmos transistor when the ouptut is at logic 0 and input is at logic 1.now to find out the transistor sizes
,equaye the currents through transistors M3 and M1.M3 is in saturation and M1 is also in saturation just equate the currents to get the sizes.u get a ration x/y ,then size x and then get y.using the same principle size the pmos transistors.
regards
Amarnath