Can I ask why digital BJTs (pre-biased) BJTs are called digital?
There is almost no source that describes why this product is so named.
Can I ask why digital BJTs (pre-biased) BJTs are called digital?
There is almost no source that describes why this product is so named.
Because it contains internal base resistors, it can be directly driven with a digital logic signal, without external resistors that are needed with standard BJT transistors when they are driven with digital logic signal.
I'd argue that Digital BJT does not exist. A BJT on it's own is an analog device, regardless of biasing.
The predominant issue with Transistor to Transistor Logic (TTL) is the connection of transistors to create a input threshold voltage. 1.4V for AS family TTL. Above this threshold (2.0V) input is considered high by transistor array. Below (0.8V), input is low. 2V and 0.8 are 0.6V up and down from 1.4V.
Now create output that follows threshold convention and output can drive inputs, which is binary logic or Transistor to Transistor Logic.
From TI's Advanced Schottky (ALS and AS) Logic Families Application Report
$$V_{Th} = V_{BE_{Q2}} + V_{BE_{Q3}} + V_{BE_{Q4}} - (V_{BE_{Q1A}}\ or\ V_{BE_{Q1B}})$$
Or approximately 1.4V for Si.
So keying off Brian Drummond's comment, it is a bit of marketing, but it has more to do with clearly identifying a new type of binary devices derived from analog devices.
Rohm Semi invented the term “digital transistors” for logic-level controlled current sinks decades ago which come pre-biased.
They are small , come in clusters or tiny in singles and are cost-effective solutions.
Unlike logic IC’s which are analog voltage controlled voltage switches with analog noise margins to guarantee switching with worst case tolerances for input and out voltage.