1 (1165)

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Step of 4 11.066P Refer to Figure P11.65 for the feedback transresistance amplifier in the textbook. Redraw the circuit by setting I, = 0 and breaking the feedback loop as shown in figure 1. Connect a voltage source of voltage as shown in figure 1. I X Y - + + 1 2 8m2 - - V. - Figure 1 Step of 4 The expression for the output voltage V. is, V. = (1) The expression for voltage V2 is, Substitute the above expression in equation (1). V. = Substitute for V. = (2) Therefore, the expression for the loop-gain of the amplifier is, Step of 4 The expression for the loop-gain of the amplifier in problem P11 is, (3) Recall equation (2). Compare the equations (2) and (3). The loop gain of the amplifier obtained by breaking the feedback loop and setting I, = 0 is more accurate when compared to the loop-gain of the amplifier in problem P11.65. This is because the value of is involved. Step of 4 Recall equation (2). Substitute for 8ml and and for and for and 64.04 for = I = 1286.5493x10³ = =155.945 The percentage difference between the two values is, %change = x100 Substitute 155.1515 for and 155.945 for (AB), %change 155.945-155.1515 x100 155.1515 =0.51% Therefore, the two values of loop gain differ by 0.51%