Electronic Technician Certification Program The OPERATIONAL AMPLIFIER OPAMP

Electronic Technician Certification Program The OPERATIONAL AMPLIFIER (OP-AMP) March 05, 2021 REVIEW Bipolar Transistor 1/11/2022 hphamett@yahoo. com 1

Electronic Technician Certification Program The OPERATIONAL AMPLIFIER (OP-AMP) March 06, 05, 2021 Inverting input • Three terminal device • inverting input to “minus” sign • Non-inverting input “plus” sign • Output • Two power supplies from +/- 8 V to +/- 38 V • IDEAL OP-AMP Vd=V(+)-V(-) • Open-Loop-Gain AOL=infinitive • input impedance zin=infinitive • output impedance zout=0 Non-Inverting input • differential input Vd= Vin(+) – Vin(-) =0 1/11/2022 hphamett@yahoo. com 2

Electronic Technician Certification Program The OPERATIONAL AMPLIFIER (OP-AMP) March 06, 2021 • PRACTICAL OP-AMP Vd=V(+)-V(-) Practical Op-amp • High voltage gain Av • Very high input impedance • Very low output impedance • Wide bandwidth 1/11/2022 hphamett@yahoo. com 3

Electronic Technician Certification Program The OPERATIONAL AMPLIFIER (OP-AMP) March 06, 2021 • Practical Op-Amp • Output voltage Vout = Vin(+) – Vin(-) x Aol = Vd x Aol • Vd = different between two inputs • The Gain (Aol) of 741 Op-Amp closed to 200000 • The output of Op-Amp is never higher than the power supplies voltage • When input applies is too high that force the op-amp into the saturation and the OP-AMP output will be equal to +/- saturation voltages ( less than power supplies about 1. 4 V ) • Open loop gain (Aol) is defined as the amplifier output amplification without any external feedback signals connected to it and for a typical operational amplifier is a about 100 decibel at DC (zero Hertz ) 1/11/2022 hphamett@yahoo. com 4

Electronic Technician Certification Program The OPERATIONAL AMPLIFIER (OP-AMP) March 06, 2021 EXAMP LE 1/11/2022 hphamett@yahoo. com 5

Electronic Technician Certification Program The OPERATIONAL AMPLIFIER (OP-AMP) March 06, 2021 1/11/2022 hphamett@yahoo. com 6

Electronic Technician Certification Program The OPERATIONAL AMPLIFIER (OP-AMP) March 06, 2021 • RF = feed back resistor between out put and inverting input to produce Closed Loop gain ACL. • No current flows into the input terminals ( high input impedance ) • The differential input is zero (Vd = V 1 -V 2=0 means V 1=V 2 ) • Closed Loop Gain ( Acl= - RF / Rin ) 1/11/2022 hphamett@yahoo. com 7

Electronic Technician Certification Program The OPERATIONAL AMPLIFIER (OP-AMP) March 06, 2021 RF Virtual GND=0 V R 1 vin + + 5 V 1 k - I + I 1. 5 k I Io vout - Vd=V(+) –V(-)=0 IL + • Current I = vin/R 1= 5 V/1 k=5 m. A • Close loop gain Acl= -R 2/R 1=1. 5 k/1 k=-1. 5 • Vout = Acl x vin = -1. 5 x 5 v = - 7. 5 v • Load current IL = 0 -(-7. 5)/5 k = 1. 5 m. A • Op-amp current Io = I + IL = 6. 5 m. A 1/11/2022 hphamett@yahoo. com RL 5 k + 8

Electronic Technician Certification Program The OP-AMP March 06, 2021 EXAMP LE For circuit shown Solve for: 1. Gain Acl =____ 2. Vout=_______ V 3. Current I through R 2=______ milli. A 4. Load current IL=______ mi A 5. Op-amp current Io=_______ milli. A 1/11/2022 hphamett@yahoo. com 9

Electronic Technician Certification Program The OP-AMP March 06, 2021 4. 5 k Vin=1. 2 vp-p 1. 5 k Vout Freq=1 k. Hz EXAMP LE For the above circuit. Solve for: 1. Closed loop gain Acl: _____ 2. Vout =_____Vp-p 3. Current I through R 1=______ milli. Ap-p 4. NOTE: the input and output is inverted or 180 degrees out of phase 1/11/2022 hphamett@yahoo. com 10

Electronic Technician Certification Program OP-AMP March 06, 2021 I R 1 - 1 k • • RF + 1. 5 k Acl= 1+ RF/R 1 Vout= Acl x vin Io = I + IL Acl always greater than 1 I Io vout Vd=V(+) –V(-)=0 v 1 + IL R 2 5 V + 1 k R 3 1 k RL 5 k Vin=v 1 x R 3 / (R 2+R 3)=2. 5 V 1/11/2022 hphamett@yahoo. com 11

Electronic Technician Certification Program NON-INVERTING AMPLIFIER March 06, 2021 • Input Vin connect to the Non-inverting input of the Op-Amp • the closed loop gain is Acl = 1 + Rf/R 2 where Rf is feedback resistor • The input and output is in-phase EXAMP • LE • For the above circuit, given Rf=1 k and R 2=1. 5 k , Vin -2. 5 VDC Solve for: 1. Gain Acl = _____ Vout=______VDC 2. Current through R 2=_____ milli. A 1/11/2022 hphamett@yahoo. com 12

Electronic Technician Certification Program OP-AMP March 06, 2021 EXAMP LE For the circuit shown. Solve for: 1. Closed loop gain Acl: _____ 2. Vout =______Vp-p if vin=2 vp-p 3. Current I through 10 k =____m. Ap-p EXAMP LE For the circuit shown. Determine the value of Rf required to produce a closed-loop voltage gain of -100 1/11/2022 hphamett@yahoo. com 13

Electronic Technician Certification Program OP-AMP March 06, 2021 • • • UNITY GAIN AMPLIFIER Another names: Buffer Amplifier, isolation amplifier, Follower Gain Acl=1 ( Vout = Vin ) 1/11/2022 hphamett@yahoo. com 14

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Electronic Technician Certification Program THE E N D 1/11/2022 hphamett@yahoo. com 32