As Lambie mentions in his comment, "gainful employment" doesn't go with "graduate school". In order to be gainfully employed you have to (in some way) make money. In more official circles (like government guidelines) it can also include other requirements.
When writing long sentences like this, you have to be careful to break up your terms and use words that don't distract from the message -- which means, first, you have to define what that message is. Here I'm going to assume this is part of a resume or CV, describing what you were taught and used as part of your graduate program, and which, presumably, have sufficient proficiency to use in a "real" job.
Given this message I would instead describe not the fields you studied, but rather the things you built based on these concepts. For example:
Using both digital and analog circuits, and well as a number of custom computer vision algorithms, my team built a poker-playing robot that could shuffle and deal a standard deck of cards, recognize the card values, move chips into a defined "pot", recognize the value of the chips in that pot, and make appropriate bets based on the value of the cards in its "hand"; additionally it could analyze the betting patterns of other players to build a "profile" for each and calculate the probability that they were bluffing.
This is a long sentence similar to the one in your example, but each of the elements coheres with those around it, so that it makes sense to the reader. Part of what makes this work is the consistency in verb tense (bolded words), which marks each of the individual elements.
If your intention is instead to simply list the different subjects covered by your graduate program, then I would break it up into the three different categories you describe:
My graduate program covered fundamental topics such as the basic laws of physics, Maxwell’s equations, lumped circuit abstractions, and amplifier abstraction, digital topics such as combinational logic, clocked systems, instructions set abstraction, high level language, operating systems, and software abstractions, and analog topics such as operational amplifiers, oscillators, power supplies, rotating machines, and power transmission and distribution.
Here the repeating "topics such as" helps break up the sentence into clearly defined subject areas, making the overall sentence simple and easy to understand as a series of three separate lists.