OpAmp-tutorial-1

Usually rin is specified in the m range in ideally

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Unformatted text preview: in the M range. in Ideally, the output resistance is zero, but the formula below gives a Ideally, more accurate value: more RoF = Ro AOL + 1 Where Ro is given for the specified device. Usually Ro is in the 10s of s range. the VCVS (Voltage Amplifier) VCVS Noninverting Configuration Example i(+) + vid vin + iO _ + i(-) _ vF _ + v1 _ iL iF RF RL + vL _ R1 i1 + vO - Given: vin = 0.6V, RF = 200 k R1 = 2 k , AOL = 400k Rin = 8 M , Ro = 60 Find: vo , iF , Av , , RinF and RoF Find: Solution: vo = vin + vinRF = 0.6 + 0.6*2x105 = 60.6 V 60.6 R1 2000 2000 Av = RF + 1 = 2x105 + 1 = 101 101 R1 iF = viin = 0.6 n R1 2000 = 1 = 1 = 9.9x10-3 9.9x10 2000 AOL 101 RinF = Rin (1 + AOL) = 8x106 (1 + 9.9x10-3*4x105) = 3.1688x1010 3.1688x10 RoF = Ro AOL + 1 = 60 60 9.9x10-3*4x105 + 1 9.9x10 = 0.3 mA 0.3 = 0.015 VCVS (Voltage Amplifier) Summary VCVS Inverting Configuration RF iF i1 vin R1 + + + _ _ RL General Equations: i1 = vin/R1 iF = i 1 vo = -iFRF = -vinRF/R1 Av = RF/R1 = R1/RF vO - The same The assumptions used to find the equations for the noninverting configuration are also used for the inverting configuration. configuration. VCVS (Voltage Amplifier) Summary Inverting Configuration Continued Input and Output Resistance Input Ideally, the input resistance for this configuration is equivalent to R 1. However, the actual value of the input resistance is given by the following formula: following Rin = R1 + RF 1 + AOL Ideally, the output resistance is zero, but the formula below gives a Ideally, more accurate value: more RoF = Ro 1 + AOL Note: = R1 This is different from the equation used R1 + RF on the previous slide, which can be confusing. VCVS (Voltage Amplifier) VCVS Inverting Configuration Example RF iF R1 i1 vin Given: vin = 0.6 V, RF = 20 k R1 = 2 k , AOL = 400k + + _ _ + vO - RL Rin = 8 M , Ro = 60 Find: vo , iF , Av , , RinF and RoF Find: Solution: vo = -iFRF = -vinRF/R1 = -(0.6*20,000)/2000 = 12 V 12 iF = i1 = vin/R1 = 1 / 2000 = 0.5 mA 0.5 Av = RF/R1 = 20,000 / 2000 = 10 Rin = R1 +...
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