Electrical – What does “driven” or “driving” mean in terms of electronics

Here is a unconventional explanation (you can find many other conventional explanations on the web)...

The basic idea is to oppose two current sources (transistor collectors); so we have to connect them in the same loop and to vary their currents in opposite directions:

As a result the voltage of the common point between the sources will "move" extremely vigorously (a fully geometrical phenomenon):

A good example of this configuration is the classic CMOS stage where the two transistors are connected with their sources to Vdd and Vss (ground) and their drains are joined:

But in the emitter-coupled (long-tailed) pair, the collectors of both transistors (T1 and T2 below) are turned up. So, we should turn the one collector (the T1's in this example) back down to stand against the other (T2's) collector. For this purpose, we have connected the simple current mirror (T3-T4) in the picture below:

See also this paper and its more sophisticated version.

It simply means that the impedance or resistance from each input terminal to the common point is equal.

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1 and 2.

• Figure 1 shows a transformer input for a balanced line microphone circuit. Clearly the input side of the circuit is symmetrical and the centre-tap is connected to ground. The impedance seen by each line will be the same and it will present itself as a load connected to a fixed potential, 0 V.
• Figure 2 is similar but this time there is a 48 V phantom power supply feeding down the two lines. Again the impedence matches but this time the reference is +48 V.

There are many more cases such as electronic differential amplifiers, etc. The main design intent is to present equal loading to both of the differential signals to prevent unbalancing the circuits which may cause a deterioration in noise and common-mode signal rejection.