Oho, I am curious about what you studied about as well.
For myself, it's Integrated circuits.
How to program digital circuits with VHDL / Verilog.
How to design circuits (Voltage Controlled Oscillators, Amplifiers, Mixers, ADCs...etc) simulate them to check their performance, draw their layout using 0.35µm CMOS and lately 180nm technologies.
Also a lot of theory on Analog electronics (differential pairs, current mirrors, noise generated...) and RF components (power amplifiers, LNAs), some reliability, the trending topics are the Internet of Things and 5G.
We covered mainly digital electronics & programming in assembly language & HLL's. We built a microcomputer, and designed & built from-scratch (etched it, etc) a transducer circuit board to interface via I/O port (i built a temperature sensor). Did CAD. Studied 741 op-amp amplifiers. Boolean logic circuits. Oscillators. A bit of everything really.