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ECE 311 Test #2 April 21 2010 Honor Code in effect Open book and notes I have neither given nor received aid on this examination. ______________________________(sign) Print your name:___________________________________ Show all work in the allotted space for each problem and circle each answer. No other material will be accepted for test answers. 1. Consider the given circuit with β = β0 = 100, VCC is 15V, VEE = -10.7V, ICQ1=1mA and R1=R2=10K. a) (5) What is the low-frequency cutoff of this circuit? b) (5) What is the voltage gain if V1=-V2? c) (5) Find VCEQ2. d) (5) Find R3. e) (5) What is the CMRR of this circuit?Print your name:___________________________________ 2. You are to design an 18W Class B public address amplifier with one input that will operate off of a single power supply and provide a (noninverting) voltage gain of 50. Assume that available op amps have a gain-bandwidth product of 1 MHz and can come within .3V of the rail voltage. A 4-Ohm speaker will be used. a) (5) If the upper frequency limit of the amplifier is to be 25 kHz, how many op amps will you need to provide the necessary bandwidth? b) (5) Draw your circuit showing component values and biasing including quiescent voltage values minimizing component count and cost. The low-frequency cutoff is to be 50 Hz and the input impedance is to be 100K. c) (5) What is the minimum value of the battery voltage that still meets the power requirement? d) (5) List what parts would you add to your circuit to provide class AB operation? Please do not draw the circuit or specify values. e) (5) What input signal is required to drive the amplifier to full power?Print your name:___________________________________ 3. Design a common-collector amplifier with ICQ = 50 mA using -10.7V and 10V power supplies. The amplifier will drive a 250 Ohm load. The amplifier will operate in class A mode and an op amp is to be used with global feedback so that the overall voltage gain is 100. a) (5) Design the current source and calculate necessary component values. b) (5) Design (draw) the amplifier giving component values so that it will operate down to DC and maximize input impedance. c) (5) Assuming that the output impedance of the op amp is 100 Ohm, what is the output impedance of the overall amplifier? d) (5) What is the maximum undistorted power output? e) (5) What is the high-frequency cutoff of the amplifier assuming that the op amp has a 1MHz gain-bandwidth product?Print your name:___________________________________ 4. (5) An important advantage of differential amplifiers is the suppression of ___________________________ noise. 5. (5) In a differential amplifier, how much improvement will there be in the CMRR if 0 is doubled? ______________________________ 6. (5) In a differential amplifier, how much improvement will there be in the CMRR if RE is doubled? ______________________________ 7. (5) When building high-gain or high-bandwidth amplifier circuits, the use of ___________________ _________________________ across the rails can significantly improve stability. 8. (5). When biasing an amplifier powered by a single power supply, the bias point should be close to half of the supply voltage to maximize


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U-M ECE 311 - ECE 311 Test 2

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