Figure 8-55(a) shows a circuit used to convert a 60-Hz sine wave to a 60-pps signal that can reliably trigger FFs and counters. This type of circuit might be used in a digital clock.

(a) Explain the circuit operation.

(b) A technician is testing this circuit and observes that the 74LS14 output stays LOW. He checks the waveform at the INVERTER input, and it appears as shown in Figure 8-55(b). Thinking that the INVERTER is faulty, he replaces the chip and observes the same results. What do you think is causing the problem, and how can it be fixed?

Figure 8-55

Transcribed Image Text:

4.7 k 74LS14 60 pps X -Otom 4.7 ΚΩ 110 V AC 60 Hz 6.3 V AC 4 V-- Vx 1 V (b)