Heavy back squats are going to make a woman out of you. If you have equipment like a belt, knee sleeves, wraps, or lifting shoes, today's the day to use them. They can help you feel more secure and supported in those heavy lifts. If you don't have any, no need to worry; just put the bar on your back. You'll still be able to move hella weight.
Dips can be done on rings, a machine, or even parallel barbells in a power rack. Use whatever equipment your gym has available. When you do them, however, try to get your elbows as close to 90 degrees as possible, and keep your elbows from flaring out.
Circuit: 3 rounds without stopping, then rest 5-10 minutes
Circuit: 4 rounds without stopping
Don't forget to write down your back-squat weight, your circuit times, what weights you used, and how you felt after finishing the workout.