rkrishnan wrote:
I am reading through the excellent book "Solid State Design" by Wes
Hayward et al. I have a specific question on Class C amplifier. On
chapter 2 Fig 15, a Clas C amplifier is shown with a buffer amplifier
link coupled in front.

Why is link coupling needed here, can't the collector be directly
connected to the base? It is for impedance matching or is there any
other motives behind this structure?

It's for impedance matching. As usual, there are several ways it can be
done, each with its own advantages and disadvantages. That method is
probably the simplest for the particular application, but you have to
watch the flux density in the transformer primary if it's wound on a
ferrite core with no air gap (such as a toroid core) and make sure the
D.C. current won't cause core saturation. Other methods allow you to
separate the RF choke from the transformer, like in Fig. 16, so you can
optimize the RF choke for its job and the transformer for its job. Or
you can use several types of LC network to do the job.

Roy Lewallen, W7EL