The TTL output stage is a rather complicated pushâpull circuit known as a totem-pole output (the transistors, diode, and resistor in the right-most slice of this TTL logic gate circuit). It sinks currents better than it sources current.
The theory for spontaneous generation refers to the idea that life can produced from nonliving things. Lazzaro Spallanzani proposed in his experiement that air was necessary for spontaneous generation.
He was professor at the universities of Modena (1763â69) and Pavia (from 1769). Spallanzani studied regeneration, fertilization, and the digestive action of saliva; using heat-sterilized cultures, he performed experiments that disproved J. T. Needham's theory of spontaneous generation.