## Engi ENGI 2132: Electronics II - Fall 2017

### Announcements

• Sample Problems for Final Exam
Results:
1-a) Vbias = 3.1 V, VCE = 4.8 V, 1-b) Vmax = 3.43 V, Vmin = -4.4 V, 1-c) PDC = 0.72 W, PAC = 0.0294 W, eta = 4.09%, 1-d) If no HS used, TJ = 47.16 C < TMAX, so no HS is needed.
2-a) Negative feedback, 2-b) 2 k Ohms, 2-c) 0.333 mA, 2-d) 4 V, 2-e) 12 V because the OA can not output a voltage higher than the supply.
3-a) Positive feedback, 3-b) Inverting Schmitt-trigger hysteresis loop with thresholds at +-6 V, 3-c) Output is a square wave, goes to -12 V when input goes greater than 6 V and +12 V when input goes below -6V.
4-a) C=3.24 nF, 4-b) high-pass filter (gain is maximum for high frequencies), 4-c) f = 49.1 kHz.
5) see class notes for Wien Bridge oscillator.
6-a) (Taking I1 = 200 uA) R1 = 52.75 kOhms, R2 = 7.5 kOhms, R3 = 14.75 kOhms, 6-b) see example in class notes, 6-c) gain = -198 (may be different depending on your values of R2 and R3)
7-a) R1 = 8.65 kOhms, 7-b) VCE1 = 6.7 V, VCE2 = 5.2 V, 7-c) acm = -0.057, 7-d) REE = 264 Ohms
8) Vin = 13V (must be greater than 11 V), must provide at least 0.608 A, Preg = 2.504 W (max), needs HS with a resistance lower than 28.4 C/W.
• Midterm Solutions
• Sample midterm exam (for practice). Correction: R2 in Problem 3 is 25 kOhms (not 2.5 kOhms).
Results: 1-a) Ic = 243 mA, VCE = 7.7 V; 1-b) Vomax = 7.4 V, Vomin = -4.56 V; 1-c) PDC = 3.645 W, PAC = 90 mW, eta = 2.46%; 2-a) PDC = 32.1 W, PAC = 22.05 W, eta=69%; 2-b) PD = 5.8 W (in each transistor); 2-c) need theta_SA < 9.8 C/W -> Use HS3 (cheapest that satisfies specs); 3-a) +-4.8 V; 3-b) R3 C = 89.3 us
• Special office hours for midterm exam: Monday, October 16th from 1pm to 2pm and from 5:30pm to 6pm.
• Midterm exam date: Tuesday, October 17th.
• Tutorial Session: Friday, September 22 at 5:30 pm in AT 1010.
• Office hours: Tuesdays/Thursdays from 2:30pm to 3:30 pm.
• Sept. 6: A practice set of problems has been posted on the Assignments page.
• Lecture times: Tuesdays/Thursdays from 1:00pm to 2:30pm in RB 1042.