The following presentation is a part of the level 5 module -- Electronic Engineering. This resources is a part of the 2009/2010 Engineering (foundation degree, BEng and HN) courses from University of Wales Newport (course codes H101, H691, H620, HH37 and 001H). This resource is a part of the core modules for the full time 1st year undergraduate programme.
The BEng & Foundation Degrees and HNC/D in Engineering are designed to meet the needs of employers by placing the emphasis on the theoretical, practical and vocational aspects of engineering within the workplace and beyond. Engineering is becoming more high profile, and therefore more in demand as a skill set, in today’s high-tech world. This course has been designed to provide you with knowledge, skills and practical experience encountered in everyday engineering environments.
4. INVERTING AMPLIFIER We can generate the following equations: Combining these gives us: This is true for any amplifier. + - Rin Vin Rf Vout Va Iin If Ia
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6. NON-INVERTING AMPLIFIER The current I flows through both resistors as no current flows into the op-amp (assumption 2) from which But Vf = Vin as the difference in input voltages is zero (assumption 1), so + - R1 Vin R2 Vout Vf I
7. or Design an amplifier that has a variable gain from 15 to 30. (use a 100K variable resistor)
8. UNITY BUFFER In the circuit Vout = Vin – what is the purpose of this circuit? + - Vin Vout
9. SUMMING AMPLIFIER (Inverting) This is a virtual earth amplifier. and Using Kirchhoff we can say: + - V2 Rf Vout Va I2 If V1 I1 V3 I3 R1 R2 R3
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11. SUMMING AMPLIFIER (Non-inverting) The output of the amplifier will be: What does V’ equal? – Use superposition theory + - V2 R1 Vout V’ V1 V3 R R R R2
12. The same is true for the other inputs so we can say: if the gain is set to 3 then: What would we get if – V1 resistor = R V2 resistor = 2R V3 resistor = 3R? V1 R R R V’
13. SUBTRACTOR (DIFFERENCE) AMPLIFIER To determine the output we will use Superposition. V1 input only V2 = 0 We have a non inverting amplifier with a gain of: + - R1 V2 R2 Vout R1 V1 R2 I
14. The voltage appearing on the + input V+ is equal to: The output is therefore input times gain: V2 input only V1 = 0 The V+ input will be at 0v and the amplifier will act as an inverting amplifier. The output will therefore be:
15. Combining these gives us the overall output equation: This circuit will take the difference between two inputs and amplify it by a factor R2/R1.
16. INTEGRATING AMPLIFIER We can generate the following equations: From what we know of op-amps we can say: V- is at earth potential (virtual earth point) The current through the resistor equals the current through the capacitor. C R Vout Vin I
17. The current through a capacitor depends upon the rate of change of voltage across it and the capacitor value. Equating gives Hence the name integrator.
18. DIFFERENTIATING AMPLIFIER We can generate the following equations: C R Vout Vin I Once again from what we know of op-amps we can say: V- is at earth potential (virtual earth point) The current through the resistor equals the current through the capacitor.
19. The current through a capacitor depends upon the rate of change of voltage across it and the capacitor value. Equating gives Hence the name differentiator.