Fig: Standard symbols and Boolean functions of the seven basic gatesFig: NAND-only realization of NOT, AND and ORFig: Functional circuit of a standard two-input TTL NAND gate. The integrated multi-emitter device Q_1 is shown as a labelled current-steering block so its distinct emitter inputs remain legibleFig: Guaranteed TTL input/output bands and the noise-margin constructionFig: Conceptual comparison of TTL output configurationsFig: Schottky-clamped BJT principle used in 74S, 74LS and later TTL