The unreliability of logic circuits of unreliable functional elements

We consider the realization of Boolean functions by circuits from unreliable functional elements in any full finite basis. We assume that each element of the circuit is exposed to arbitrary faults, and the elements faults are statistically independent. We show that any Boolean function can be realized by a circuit the unreliability of which is not more than 5.17 times greater than the unreliability of “worst” (the most unreliable) element from the basis.