"TTL" is an abbreviation for Transistor-Transistor Logic. It describes an IC technology for making logic circuits using NPN bipolar transistors. [https://en.wikipedia.org/wiki/Transistor–transistor_logic](https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logic) The exact structures, dimensions and processes used to make the transistors in TTL ICs varies from one manufacturer to another according to their proprietary silicon foundry process. Therefore there is no such thing as a discrete "TTL" transistor. So, what do you mean? Please explain your question in more detail.

If what you mean is a transistor that turns on and off with TTL logic levels, look for logic transistor on the NXP (or maybe Nexperia) website.  Zetex also do some.

And OnSemi: [https://www.onsemi.com/PowerSolutions/parametrics.do?id=799&tab=products](https://www.onsemi.com/PowerSolutions/parametrics.do?id=799&tab=products) Suppliers: [https://uk.rs-online.com/mobile/c/semiconductors/discrete-semiconductors/digital-transistors/](https://uk.rs-online.com/mobile/c/semiconductors/discrete-semiconductors/digital-transistors/) [https://uk.farnell.com/webapp/wcs/stores/servlet/Search?categoryId=700000102004&pageSize=25&catalogId=15001&langId=44&st=Digital+Transistors&storeId=10151](https://uk.farnell.com/webapp/wcs/stores/servlet/Search?categoryId=700000102004&pageSize=25&catalogId=15001&langId=44&st=Digital+Transistors&storeId=10151)

@andyfierman Yes that's them.  And available in packs of 50 for 0.7p (1 US cent) each !    Usually you have to buy thousands to get that price.   And to think my first transistors (2G371 * 2 for a multivibrator) cost 5/- each !

Or use a logic level MOSFET... [https://www.digikey.com/catalog/en/search?filters=53168](https://www.digikey.com/catalog/en/search?filters=53168) [https://www\.bitsbox\.co\.uk/index\.php?main\_page=product\_info&cPath=140\_151\_154&products\_id=1059](https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=140_151_154&products_id=1059)