Question

c) In estimating DC imperfections (input offset voltage, input offset current and the inverting amplifier with nominal gain of -100 using 1 current) of an op-map, an and 10MQ resistors is implemented using the op-amp as shown in Fig 2(a) below R2 10MQ R 100k Vi Vo Figure 2(a): Inverting amplifier Measurements are conducted on the output voltage of the inverting amplifier under the following conditions: (i) the input (V) is open circuited and the output voltage is found to be +9.31V ; (ii) the input (V) is grounded and the output voltage is found to be +9.09V; ii the inverting amplifier is further modified by connecting resistor between the positive input terminal and ground (shown in Figure 2(b)) and the output voltage is measured to be -0.8V with the input (V) opened. What are the estimate values of the input offset voltage, input offset current and input bias current of the op-amp? a 10MQ [30 Marks] R2 10M RI 100k O Vo Vi R 10MQ Figure 2(b): Modified inverting amplifier d) Using imperfection values obtained in (c), calculate the worst output offset voltage for the amplifier circuit of figure 1 configured as difference amplifier. [20 marks] The circuit in figure 1, with Ri R2=R3=R4=25KQ, can be configured for a variety of applications by the appropriate connection of terminals A, B, C, D, and O. R2 R1 AO W BO R4 R3 Figure 1

Answer 1

Raz1omn RiE100kn given by AoL =- 4Oo Zi00, . gain ie finite. we knou that No=Aava wheve Na -Vx-Vが Na-V heNo 100N we Knou that Vio VV impat offee t Voltage is di fference f mon-inverting Noltage to inveting Valtage given b a V= oren ccut Vo.3 AV Pava, Vo RoL( ) -400 (0-) g.34 9.34 RN ニ0934 then input offset Noltage Vio =Vx-V =0-Ny=-と \vial = IVッ\- .09 31 Vo 3Tounded, No- 9.0gv AoLVa Vo 00-y) No= Vo A00Vy

.0g then input offeet Nltagte Vio 1viol 0309 We find inpat offset carrent. Cant find input offfet cunent and input bias carrent in fig a(a because this figue we 0Astan ce in mon-inverHng texminal ave mot ave nat fNor) tis ciseuit R-Lon 1.60kM VioNMN Va Voこ Rニ Va=-4o0(0-) No-L00Ny .given bg Voニ. f ac) Va 008 he input 0ffset Vattage Nio N-y Vio ニーVy

Rd-4ookip 二10 mn No It Lomin A+ Ka N。ニー スfRA + RA -TR2+TRA R さo Ra No- -.a Lo mn O HA 13-1 Tbias Vo=Ibiag メRe .ias + I =00MA