AMPLIFICADORES + VI = VS + VG - (S N ) = VV VI VG VS IS = I IG VS VS VG + VIS = VS - VG = 0 VI VG VS RC1 VS RC2 VI VG V I G = V G' ⋅ V G' = V G ⋅ zs RI - zs V IS = V S ⋅ + RC1 VG (Z S RI // R C 2 ) + R C 1 + R I (Z S RI // R C 2 ) + R C 1 + R I RC 2 RC 2 + Z S RC2 RI VI V2 + Vi2 Vi1 + Vd/2 Vo2 - + Vc Vo1 + Vd/2 V1 V d = V 2 − V1 ; Vc = V2 + V1 2 Vo2 Vi2 Vod = ADD ⋅ Vid + ADC ⋅ Vic A Vi1 Voc = ACD ⋅ Vid + ACC ⋅ Vic Vo1 CM RR = E = ADD ADC AC D ADD Vic Vod = ADD Vid + CMRR EN UN AMPLIFICADOR “SINGLE ENDED” (Vo1= 0) SOLO ESTÁN DEFINIDAS ADD Y ADC. V0 = AD ⋅Vid + AC ⋅Vic AMPLIFICADORES DE INSTRUMENTACIÓN v1 R2 + - RG v2 R1 + R R vo R3 R 2R VO = (V2 − V1 ) 2 + 1 R1 RG R2 R4 = R1 R3 R4 + RG R4 R3 + + v1 R2 R1 vo R R VO = (V2 − V1 ) 1 + 2 + 2 2 R1 RG R1 = R3 ; R2 = R4 v2 R2 v1 R1 + v2 R3 vo V = (V − V ) ⋅ R2 2 1 O R1 R4 R2 R4 = (0,1% ⇒ CMRR ≤ 66 db) R1 R3 EJEMPLO: PUENTES DE MEDIDA V R4 R3 R1 R2 V = − V = R 2 + R3 R1 + R 4 o Vo R2 R1 Si Si y R 4 R3 − R1 R 2 V = R 4 R3 1 + 1 + R R 1 2 R 4 R3 = R1 R 2 V =0 o R1= R2= R4= R (un solo elemento variable) R3=R(1+ δ) V = o Si y δV 2(2 + δ ) R2= R4= R R1= R3= R(1+δ) (mayor sensibilidad) 1 − (1 + δ ) 2δ V = V≅ V (2 + δ ) δ +1 2 2 o Si R1= R4= R y R2= R(1+δ) R3= R(1-δ) δ V = V 2 o CIRCUITO EQUIVALENTE. R2 2 Vd R R1 R V 1 2 R 1 Vc R(1 + δ ) V δ 2 (2 + δ ) V Vc = 2 Vd = R1 = R 2 R2 = R 1+ δ 1− δ R2 2 + R (1 − δ ) R (1 + δ ) 1 2 V Vd + Vc Vd R1 1 R (1 + δ ) R (1 − δ ) V δ 2 V Vc = 2 Vd = (1 − δ ) 2 R1 = R 2 = 2