1 ECE2100 Exam 1 This is a closed book, and notes exam. You may have one page of notes(front and back), pencil(s), pen(s), eraser(s) and a calculator. NAME:________________________________________________ I certify that the work below is my own. Signature: _______________________________________________2 Problem 1 – (43 points) • Both amplifiers have the following characteristics: Avo=40 Ri=2kΩ Ro=4kΩ Clipping levels: L= 12V (unloaded) (a) Redraw this 2 stage amplifier using the amplifier model. Make sure to label V1, V2, V3, and VL on the schematic. (15 points) 1kΩ 2kΩ 2kΩ 100Ω V1 V2 V33 1. (cont.) (b) Find Av= . Express your answer as a ratio(V/V) and in dB. [Round the answer to a whole number] (10 points) (c) For the input VS as shown, sketch (make the peaks exact and estimate between the peaks) the output at VL on the graph below. (8 points) (d) Evaluate the overall current gain. ( ) [round to the nearest whole number and express as A/A]. (10 points) vLVs4 Problem 2 – (20 points) Sketch the straight-line approximation of the Bode (both magnitude & phase) plot for: (make sure to label all your y values) H(s)= .( )s 100 ( )s 1k.( )s 10 ( )s 10k (rad/sec.) (rad/sec.) degree dB |H(s)|5 Problem 3 – (37 points) (a) Assume all operational amplifiers are ideal V1=10mVpp, V2=20mVpp, V3=50mVpp (i) What is the voltage value at Vo1(express as Vpp)? (10 points) (ii) What is the voltage value at Vo (express as Vpp)? (10 points) 1k 2k 4k V1 V2 V3 20k 20k 20k 20k 10k 10k 1k R1=570 Vo16 (b) All operational amplifiers are NOT ideal and have the following characteristics: Input offset voltage: Vios=2.0mV Input offset current: Ios=100nA Input bias current: IiB=500nA Input resistance: Ri=2MΩ Output resistance: Ro=75Ω Open-loop gain: Ao1=100dB Unity-gain bandwidth: fT=4MHz Output swing limits: L= 12V Slew rate: SR=2V/µs (i) Explain the purpose of the R1 resistor? (5 points) (ii) When V1=V2=V3=0 calculate the voltage that will be observed at Vo1. (12 points) {Hint: there are two effects} 1k 2k 4k V1 V2 V3 20k 20k 20k 20k 10k 10k 1k R1=570 Vo12 Problem 1 – (25 points) Assume both diodes are identical and ideal. Verify that your assumption for the diode operation(i.e. on or off) are correct. a) 9 points – The current I1 b) 9 points – The current I2 c) 7 points – The voltage Vo 1k2kD11kD2+ - I I1 I23 Problem 2 – (25 points) Referring to the pn junction diode, determine the following: (5 points each) 1) For p-type material: a) The majority carrier(holes or electrons) is_________________________ b) As the temperature DECREASES, what happens to the number of MAJORITY carriers in this p-type material? 2) For p-type material: a) The minority carrier is_________________________ b) As the temperature DECREASES, what happens to the number of MINORITY carriers in this p-type material? 3) As the temperature INCREASES, what happens to the number of unbound holes in the n-type material? 4) As the temperature INCREASES, what happens to the reverse saturation current IS? 5) Explain how the diffusion current, ID, is created.4 Problem 3 – (10 points) a) Use the constant voltage drop diode model with VD0=0.7 i) 2.5 points – Solve the circuit for I ii) 2.5 points – Solve the circuit for Vo b) Use the piecewise linear diode model with VD0=0.7 and rD=20Ω iii) 2.5 points – Solve the circuit for I iv) 2.5 points – Solve the circuit for Vo D12kD2I5 Problem 4 – (15 points) Given Vs=15 + 3sin(ωt) V Assume VD=0.7V, n=2, and VT=25mV Assume identical diodes Use the constant voltage drop method when appropriate c) 3 points – Determine the DC component of the diode current, ID. d) 3 points - Determine the DC component at the output, Vout. e) 3 points – Determine the AC component of the diode current, id. f) 3 points - Determine the AC component at the output, Vout. g) 3 points – What is the total output for Vout. VsRVout + - Vs 1k ID1 ECE2100 Exam 1 This is an open book, and notes exam. You may use a calculator. NAME:________________________________________________ Alias to be used to post grades outside my door (leave blank if you would not like it posted: (do not use any part of your SSN or uID number) _______________________________________________ I certify that the work below is my own. Signature: _______________________________________________2 DC = 10VD3DC = 5V1m1kD1D21kProblem 1 – (30 points) Assume all diodes are identical and have VDO=0.7V. Use the constant voltage drop method. Verify that your assumption for the diode operation(i.e. on or off) are correct. Find the following making sure you find the correct operation of the diodes. a) State your assumptions (diode is on/off): b) The current I1 c) The current I2 d) The current I3 e) The voltage Vo f) Your verification: I1 I2 I3 Vo D23 DC = 10VD3DC = 5V1m1kD1D21k I1 I2 I3 Vo D24 Problem 2 – (25 points) a) Sketch the Bode (both magnitude & phase) plot for: {label your axis and show all your work} H(s) = ()()( )( )000,1010100)100(2+++ssss b) What is the estimated magnitude value at ω=1 rad/sec: c) For the magnitude plot, what is the slope of the line going through ω=1 rad/sec: d) What is the estimated phase value at ω =1 rad/sec: e) For the phase plot, what is the slope of the line to the left of ω =1 rad/sec: f) For the phase plot, what is the slope of the line to the right of ω =1 rad/sec: g) List the three frequencies other than 0 where the bode plots will have a change in slope (or value):5 H(s) = ()()( )( )000,1010100)100(2+++ssss6 Problem 3 – (25 points) (a) For the circuit above, assume all operational amplifiers are ideal 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2-0.01-0.008-0.006-0.004-0.00200.0020.0040.0060.0080.010 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2-0.1-0.08-0.06-0.04-0.0200.020.040.060.080.1 (i) What is the voltage value at Vo1(express as Vpp)? (ii) What is the voltage value at Vo (express as Vpp)? 8k 2k V1 Vo1 A1 Vo V2 20k 20k 10k 10k 10k 10k 2k Input V1 Input V27 (b) Assume