fast TTL interface

63 fast TTL interface It is surprising how often TTL ICs are asked to perform a difficult (if not impossible) task. It is, of course, gratifying to know that experimenters have so much confidence in the capabilities of the TTL logic family. But, on the other hand, why drive the devices to extremes when they are not likely to sur- of this type of vive? More often than not the outpu mistakenlly, to IC is overloaded, or they are used, t case, the switch until the input level has reached approxim- ately half the supply level, unless the manufacturer has taken the appropriate measures to avoid this. As a result, a delay of about 40 ns will be incurred and the poor signal edge at the input is bound to lead to a far optimum edge at the output. In the case of the lower signal shown, an effort has been made to improve the positive-going edge by including a pull-up resistor between the TTL output and the positive supply voltage. This resistor (220 SI) will certainly improve the positive-goi...