reproducible delay

elektor july/august 1983 14 reproducible delay There are many occasions when a switching delay is required. One way of achieving this is to use an RC network and an inverter (see figure 1). This is quite practical and obvious as there are nearly always some gates left over" in a circuit. Unfortunately, every electronic component has a definite tolerance and so it is vir- tually impossible to determine the delay precisely in advance. However a considerable improvement can be achieved by connecting two inverter/ RC networks in series as shown in figure 3. 3 half the supply voltage. Further, The nominal threshold voltage of the inverter in figure 1 is half the supply voltage and has a tolerance of ± 30%. Figure 2 shows the signa) input to the Bate. 1f this input is between Uc= 0.35 Ub and Uc= 0.65 Ub the inverter may consider it either logic "0" or "1"! These voltages occur when a capacitor is charged through a resistor after a period of 0.43 T and 1.05 T respectively. (T is the tim...