EECE 310 Homework 1, Fall 2011

American University of Beirut Department of Electrical and Computer Engineering EECE 310 – Electronics Fall 2011 – 2012 Homework 1 Due Wednesday October 5, 2011 at 9:00 am Problem 1. [50 points] An amplifier has the transfer characteristic: vO = 12 – 10 (vI – 3)2 V. where vO and vI are in volts. This transfer characteristic applies for 3 < vI < vO + 3 V, and vO positive. At the limits of this region, the amplifier saturates. a) [15 points] Sketch and clearly label the transfer characteristic. What are the saturation levels L+ and L– and the corresponding values of vI? b) [10 points] Bias the amplifier to obtain a DC output voltage of 6 V. What value of input DC voltage VI is required? c) [10 points] Calculate the value of the voltage gain (in V/V and in dB) at the bias point. d) [15 points] If a sinusoidal input signal is superimposed on the DC bias voltage VI, that is: cos( ) I I i v V V ωt = + , find the resulting vO. Express vO as the sum of a DC component, a signal component at ω with amplitude A1 and another component at 2ω, with amplitude A2. The component at 2ω is undesirable and is the result of the nonlinear transfer characteristic of the amplifier. If it is required to limit the ratio 2 1 A A to 1%, what is the corresponding upper limit on Vi? Problem 2. [50 points] An amplifier operating from +/– 12.7 V power supplies has a linear transfer characteristic except for output saturation at +/– 11 V. a) [12 points] The peak-to-peak value of the largest sinusoidal wave that can be applied at the amplifier input without output distortion is 0.5 V. Find the amplifier voltage gain in V/V and in dB. b) [8 points] What is the corresponding output power for an 32 Ω load? c) [20 points] What is the power gain, in W/W and in dB, if the input power is 10 mW? What is the current gain of the amplifier, in A/A and in dB? d) [10 points] What is the amplifier efficiency (in %) if the DC current drawn from each power supply is 200 mA?