Radio Frequency Integrated Circuit Design - Webs

LNA Design
Figure 6.31 Illustration of nonlinearity in the common-collector amplifier.
If this is the case, then there will be no clipping of the waveform.
The linearity can be improved by increasing IB or R out. This will continue
to improve performance as long as power supply voltage is large enough to
allow this swing. Thus, for large R out, the power supply limits the voltage swing
and therefore the linearity. In this case, the current is not a limiting factor.
6.5 Differential Pair (Emitter-Coupled Pair) and Other
Differential Amplifiers
Any of the amplifiers that have already been discussed can be made differential
by adding a mirrored copy of the original and connecting them together at the
points of symmetry so that voltages are no longer referenced to ground, but
rather swing plus or minus relative to each other. While this is hard to describe,
it is easy to show an example of a differential common-emitter amplifier (more
commonly called a differential pair or emitter-coupled pair) in Figure 6.32. Here
the bias for the stage is supplied with a current source in the emitter. Note that
Figure 6.32 Differential common-emitter amplifier or emitter-coupled pair.
183