The university of iowa fall 2011 question 8 an op amp

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 11. Question 8 An op-amp is ideal except that it has a finite open-loop gain . The op-amp is connected in an inverting configuration using two resistor and . (a) Show that the closed-loop gain is ( ) (b) Determine ⁄ such that the closed-loop gain is the open-loop gain is ? (1 5 points) . (b) What is the closed-loop gain if Solution Part (a) Consider the inverting amplifier shown. KCL at the inverting input gives ( ⁄ Note that with finite gain, so that or , but since , . Thus, the KCL equation becomes ⁄ ⁄ ( ⁄ Solving for the closed-loop gain )( yields the desired expre ssion: ( Part (b) Set Part (c) Using and ⁄ ) and solve to find and yeilds 9 ) ⁄ 55:041 Electronic Circuits. The University of Iowa. Fall 2011. Question 9 In the noninverting op-amp amplifier shown, the op-amp is ideal except for a finite open-loop gain and differential-mode input resistance (a) Draw an equivalent model that uses a voltage -controlled voltage ⁄ . (b) source and use the model to derive an expression for Use the model to derive an expression for the input resistance (c) Calculate and for and (1 5 points) This problem is poorly-posed and will not be graded 10 55:041 Electronic Circuits. The University of Iowa. Fall 2011. Question 1 0 The circuit shown is a representation of the common-mode and differential-input signals to a difference amplifier. One can write the output voltage as , where is the differential-mode gain and is the common-mode gain. Assuming an ideal op-amp, one can show that the common-mode gain is ( ) ( ⁄ Further, if , and one can show that the differential-mode gain is | | circuit above, , and . If the tolerance of each resistor is determine the minimum CMRR (in dB). ⁄ . For this , Hint: consider using tools such as Excel or Matlab to search for the resistor combination that result in minimum CMMR. (1 0 points) Solution | This will have minimum value when | spreadsheet the largest is when | is the largest | ( ( ( ( | | is the smallest. Using an Excell ( ( ( ( Then ( ( Further...
View Full Document

This note was uploaded on 10/26/2013 for the course ECE 55:041 taught by Professor Kruger during the Fall '11 term at University of Iowa.

Ask a homework question - tutors are online