output nodes of a prior inverter an output node 626 and an output node 634 are coupled to inputs of a subsequent inverter as shown in fig5 b input 629 is coupled to mosfet 623 and is also coupled to a gate 628 of mosfet 622 similarly a node 625 of inverter 631 is coupled to mosfet 624 at a gate 630 and is also coupled to output node 626 the rise to fall ratio from input 629 to output 634 for the circuit of fig5 b was found to be about 1 5 1 this characteristic makes the circuit in fig5 b better qualified than the circuit in fig5 a to propagate high frequency pulse trains fig5 c shows a circuit where two inverters 114 and 116 are coupled varying a voltage vc 5 applied to an input 118 varies resistance across a depletion type mosfet 102 and a depletion type mosfet 104 which both function as variable current sources an input node 98 and an input node 100 are coupled to outputs nodes of a prior inverter a voltage v 100 on input node 100 is an inverse of a voltage v 98 on input node 98 i e when v 98 is at logic 1 then v 100 is logic 0 and vice versa a depletion type mosfet 106 and an enhancement type mosfet 110 of inverter 114 are coupled as.