<^< Differential Amplifier | Course Index | Direct Coupled Amplifier >^>
Objective:
| To investigate a differential operational amplifier.
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Underpinning knowledge:
| Operational amplifier symbols and connections.
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Apparatus:
| TINA circuit file, or apparatus to make the following circuit.
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TINA Circuit File:
| Click here to download circuit file
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Initial Settings:
| Vin1 = Vin2 = 0V, R1 = R2 = 100kΩ, R3 = R4 = 500kΩ
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Requires:
| Paper, Linear graph paper, pen or pencil.
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Instructions:
(a) Set R1 = R2 = 100kΩ and R3 = R4 = 500kΩ
(b) Set Vin1 and Vin2 to 0V
(c) Measure and record the values of Vin1, Vin2 and Vout (using VM1).
(d) Repeat (c) for each of the following conditions:
- Vin1 = +1V and Vin2 = 0V
- Vin1 = 0V and Vin2 = +1V
- Vin1 = -1V and Vin2 = 0V
- Vin1 = 0V and Vin2 = -1V
- Vin1 = +1V and Vin2 = +1V
- Vin1 = -1V and Vin2 = -1V
(e) Set R1 = R2 = 100kΩ and R3 = R4 = 1MΩ
(f) Repeat (b) to (d) above.
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Observations:
(a) Comment on the results obtained.
(b) Show that the output voltage, Vout, of the amplifier is given by: Vout = -RF/Rin x (Vin1 - Vin2) where RF = R3 = R4 and Rin = R1 = R2
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Further work:
With R3 = R4 = 1MΩ and R1 = R2 = 100kΩ, use the data obtained earlier to plot a graph showing the relationship between Vout and (Vin1 - Vin2). What does the slope of this graph indicate?
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