operational_amplifiers-2p - Operational Amplifiers...

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1 Operational Amplifiers (Op-Amps) Basic Op-Amp Operational amplifier or op-amp, is a very high gain differential amplifier with a high input impedance (typically a few mega ohms) and low output impedance (less than 100 ohms). Note the op-amp has two inputs and one output.
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2 1 2 i i d V V V = Ideal Op-Amp Properties 1. Infinite Input Resistance: R i = 2. Zero Output Resistance: R o = 0 3. Infinite Voltage Gain: A d = 4. Infinite Bandwith: BW = 5. Infinite output current 6. Perfect Balance i.e. V o = 0 when V i1 = V i2 7. Above characteristics do not drift with temperature
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3 MC1530 Operational Amplifier 1 B EE 1 0 R 7 . 0 V V I I 1 + = = () V 14 . 3 R R R 7 . 0 2 V V 5 4 5 EE B 1 = + × + = mA 99 . 0 I 0 = mA 495 . 0 2 I I I 0 C C 3 2 = = = 6 B 6 E 6 R 7 . 0 V R V I 4 4 = = V 18 . 2 I R V V 3 4 C 3 CC B = = mA 986 . 0 I 6 = mA 493 . 0 2 I I 6 C 5 = = V 52 . 4 I R V V 5 C 7 CC 3 = = V 82 . 3 7 . 0 V V 3 4 = = DC Analysis (MC1530 ) mA 56 . 1 R V V I I 8 D EE C 8 3 7 = = V 7 . 0 V V , 1 , 100 h h D BE FE fe = = = α = =
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4 Output stage 9 B C 10 I I I I 8 7 = 10 10 B o R I V v 8 + = V 6 . 4 V 7 . 0 7 . 0 V EE B 8 = + = mA 4 . 1 R V V I 9 B 9 8 4 = = V 0 mV 200 v o = mA 16 . 0 I 10 = AC Analysis (MC1530 ) V 7 . 0 V V , 1 , 100 h h D BE FE fe = = = α = = 2 2 1 ie L fe d 1 2 v h R h A 2 V V A = = = Ω = = = k 12 . 3 h || R h || R R 3 ie 3 ie 2 L 4 2 60 A 1 v = Ω = = k 2 . 5 h h h 4 2 ie 3 ie ie 9 . 28 h 2 R h A V V A 4 2 ie 7 fe d 2 3 v = = = = 1 V V A 3 4 v 3 = 5 R R V V A 9 10 4 o v 4 = =
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5 Improvements Op-Amp Gain Op-Amps have a very high gain. They can be connected open- or closed loop. Open-loop refers to a configuration where there is no feedback from output back to the input. In the open-loop configuration the gain can exceed 10,000. Closed-loop configuration reduces the gain. In order to control the gain of an op-amp it must have feedback. This feedback is a negative feedback. A negative feedback will reduce the gain and improve many characteristics of the op-amp.
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6 Inverting Op-Amp The input is applied to the inverting (-) input; the non-inverting input (+) is grounded. The resistor Rf is the feedback resistor; it is connected from the output to the negative (inverting) input. This is negative feedback . Virtual Ground An understanding of the concept of virtual ground provides a better understanding of how an op- amp operates.
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This note was uploaded on 05/25/2011 for the course ELECTRONIC 311 taught by Professor Umutsezen during the Fall '11 term at Hacettepe Üniversitesi.

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operational_amplifiers-2p - Operational Amplifiers...

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