Chegg Solutions for Microelectronic Circuits (Adel S Sedra, Kenneth C Smith) (Z-Library)_parte_1076

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Step of 4 9.122P Refer to Figure 8.43 in the textbook for a four-stage bipolar op-amp. Consider the following expression for the output resistance: The term, value depends on the value of current gain, If the value of changes the value of B+1 this term, the value of the term with series combination of changes and hence the entire value of output resistance changes. Therefore, the value of resistor, effects the output resistance. Step of 4 Consider that the output resistance reduced by a factor 2. Consider that the output resistance, = Therefore, 76 Ω Here, Substitute 3 kΩ for 76 R' +3000 = +228000 228000 228000 2924 = 77.975 Ω The resistance, is, Substitute 100 for the current gain, 77.97 Ω for and for = Therefore, the new value of resistor, is, 7.37 Step of 4 Calculate the change in gain at third stage of the amplifier due to the change in resistance. = Substitute 7.37 kΩ for 303.5 kΩ for 25 Ω for and 2300 Ω for R, = (7.37 kΩ + 303.5 MΩ = kΩ) 2236.795 = 722.77 = -3.094 V/V Calculate the third stage gain with = 15.7 kΩ Substitute 15.7 for 303.5 for 25 for and 2300 Ω for R, = (15.7 4764.95 MΩ = kΩ) 4764.95 = 742.14 = -6.42 V/V Step of 4 Calculate the value of overall gain. Substitute 8513 V/V for Aold -3.094 V/V for and -6.42 V/V for A30 A (8513 V/V) -3.094 -6.42 V/V V/V = (8513 V/V)(0.482) = 4103.3 V/V Thus, the value of overall gain is 4103.3 V/V The factor of gain change is, 8513 4103.3 2.075 Therefore, the gain reduced by factor of 2.075 for the change in output resistance by a factor of 2. To maintain the amplifier as same value, reduce the resistor, R, by a factor 2.075. Thus, the resistor value is, 2.3 2.07 1.11 Therefore, by reducing R4 value to it is possible to maintain the gain at 8513.