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An amplifier is designed so that it amplifies a differential input signal by a factor of 100 and it attenuates a common-mode signal by a factor of 10 . What is the CMRR of the amplifer in dB ? 80 dB 60 dB 40 dB

An amplifier is designed so that it amplifies a differential input signal by a factor of 100 and it attenuates a common-mode signal by a factor of 10 . What is the CMRR of the amplifer in dB ? 80 dB 60 dB 40 dB

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An amplifier is designed so that it amplifies a differential input signal by a factor of 100 and it attenuates a common-mode signal by a factor of 10 . What is the CMRR of the amplifer in A B ? 80 d B 60 d B 40 d B

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Q1. Consider the idea amplifier shown with voltage gain = −G, Zin → ∞ and Zo → 1000 a) Find the poles of the circuit and the cutoff frequency in Hz if, R1 = R2 = R3 = 1 kΩC1 = C2 = 12π nF b) The total gain in this circuit is G2, if we add more stages such that the total gain stays the same but we want to bandwidth to improve by a factor of 10 . What will be the gain of a single stage consider that the total number of stages is now 10 . Show your equations.
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Nonideal (i.e., real) operational amplifiers respond to both the differential and common-mode components of their input signals (refer to Fig. 2.4 for signal representation). Thus the output voltage of the op amp can be expressed as vO = AdvId +AcmvIcm where Ad is the differential gain (referred to simply as A in the text) and Acm is the common-mode gain (assumed to be zero in the text). The op amp’s effectiveness in rejecting common-mode signals is measured by its CMRR, defined as CMRR = 20 log|Ad/Acm| Consider an op amp whose internal structure is of the type shown in Fig. E2.3 except for a mismatch ∆Gm between the transconductances of the two channels; that is, Gm1 = Gm – 1/2∆Gm Gm2 = Gm + 1/2∆Gm Find expressions for Ad , Acm, and CMRR. What is the maximum permitted percentage mismatch between the two Gm values if a minimum CMRR of 60 dB is required?

Nonideal (i.e., real) operational amplifiers respond to both the differential and common-mode components of their input signals (refer to Fig. 2.4 for signal representation). Thus the output voltage of the op amp can be expressed as vO = AdvId +AcmvIcm where Ad is the differential gain (referred to simply as A in the text) and Acm is the common-mode gain (assumed to be zero in the text). The op amp’s effectiveness in rejecting common-mode signals is measured by its CMRR, defined as CMRR = 20 log|Ad/Acm| Consider an op amp whose internal structure is of the type shown in Fig. E2.3 except for a mismatch ∆Gm between the transconductances of the two channels; that is, Gm1 = Gm – 1/2∆Gm Gm2 = Gm + 1/2∆Gm Find expressions for Ad , Acm, and CMRR. What is the maximum permitted percentage mismatch between the two Gm values if a minimum CMRR of 60 dB is required?
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For a differential amplifier shown below, we may define CMRR OA as the common-mode rejection ratio of the op-amp itself, and CMRRR = 12(2 R2 R4+R2 R3+R1 R4 R1 R4−R2 R3) as a kind of CMRR to account for the resistance variations. Then it can be shown that the CMRR of the differential amplifier circuit, CMRR0 is given as CMRRD = CMRRRCMRROA+1 /4 CMRRR+CMRROA When CMRRRCMRROA≫1 /4, then a useful relationship is 1 CMRRD≈1 CMRRR+1 CMRROA (a) Show that when R2 = R4 and R1 = R3 then CMRRR→∞, and CMRRD = CMRROA. (b) Now assume that R2≈R4 and R1≈R3. Given that resistors have tolerances |δRR| < t, show that the worst-case CMRRR is CMRRR≈GD+14 t, where GD is the differential gain of the circuit. (c) For a 0.1% tolerance on resistance values, and a gain of 100 , compute the worst-case CMRRD when CMRROA is 100 dB. How about when the resistor tolerances are only 1% ? (d) Show that if R4 is replaced by a potentiometer (a variable resistor) then CMRRD may be optimized

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