An R–C coupled amplifier is assumed to have a singlepole

An R–C coupled amplifier is assumed to have a singlepole low frequency transfer function. The Maximum lower-cut -off frequency allowed for the amplifier to pass 50 Hz square wave with no more than 100% till is:

Fractional tilt =	πf_L
	f

where, f_L = Lower cut-off frequency
f = applied signal frequency

or f_L =	f × fractional tilt
	π

or f_L =	50 × 10/100
	3·14

= 1.59 Hz