Attention in TTL use: Generally, TTL level overshoot will be serious, and a 22 ohm or 33 ohm resistor may be connected in series at first; When the TTL level input pin is suspended, it is considered high internally. If you want to pull down, use a resistor below 1k to pull down. TTL output cannot drive CMOS input.

Precautions for ECL, PECL and LVPECL: Different levels cannot be directly driven. The middle can be converted by AC coupling, resistance network or special chip.

The above three types are emitter follower output structures, and a resistor must be pulled to DC bias voltage. (such as LVPECL, often used for clocks: used for DC matching.

Pull up 130 Euro and pull down 82 Euro; Ac matching time

Start with 82 Euler and use 130 Euler at the same time. However, after two modes of operation, the DC level is about1.95v. )