Editing Differential amplifier (section)

==== Collector current mirror ====

The collector resistors can be replaced by a [[current mirror]] (the top blue section in Fig.&nbsp;3), whose output part acts as an [[active load]]. Thus the differential collector current signal is converted to a single-ended voltage signal without the intrinsic 50% losses, so the gain is doubled. This is achieved by copying the input collector current from the left to the right side, where the magnitudes of the two input signals add. For this purpose, the input of the current mirror is connected to the left output, and the output of the current mirror is connected to the right output of the differential amplifier.
[[File:Diffential amplifier transimission charackteristic.svg|thumb|Figure 4: Transmission characteristic{{Clarify|reason=The current I_ABC needs to be identified.|date=June 2023}}]]
The current mirror copies the left collector current and passes it through the right transistor that produces the right collector current. At this right output of the differential amplifier, the two signal currents (pos. and neg. current changes) are subtracted. In this case (differential input signal), they are equal and opposite. Thus, the difference is twice the individual signal currents (Δ''I''&nbsp;−&nbsp;(−Δ''I'') = 2Δ''I''), and the differential to single-ended conversion is completed without gain losses. Fig.&nbsp;4 shows the transmission characteristic of this circuit.