Hcu/Hct-Based Oscillator

When frequency stability is not of prime importance, a simple, yet reliable, digital clock oscil- lator can be made with the aid of relatively few components. High-speed CMOS (HCU/HCT) inverters or gates with an in- verter function are eminently suitable to make such oscil- lators, thanks to their low power consumption, good output sig- nal definition and extensive fre- quency range. The circuit as shown uses two inverters in a 74HCT04 or N1, N2 = 1/3 IC1 = 74HCT04, 74HCU04 87437 both resistors can be realized as presets to enable precise set- ting of the output frequency and the duty factor. Do not forget, however, to fit small series resistors in series with the presets, in observance of the minimum values for R and Rs as given in the design equa- tions. The values quoted for lc are only valid if the inputs of the remaining gates are grounded. Source: Philips CMOS Designers Guide, January 1986, p. 105 ff. St HCU/HCT-BAS SCILLAT R 74HCU04. The basic design equations are for HCU: ...