<^< Voltage Gain | Course Index | Input Resistance >^>
| Objective:
| To investigate the voltage gain of an 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
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| Requires:
| Paper, Linear graph paper, pen or pencil.
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| Instructions:
(a) Set Vin1 (the voltage at the '+' terminal) and Vin2 (the voltage at the '-' terminal) to 0V
(b) Measure and record the values of Vin1, Vin2 and Vout (using VM1).
(c) Repeat (b) for each of the following conditions:
- Vin1 = +5mV and Vin2 = 0V
- Vin1 = 0V and Vin2 = +5mV
- Vin1 = -5mV and Vin2 = 0V
- Vin1 = 0V and Vin2 = -5mV
- Vin1 = +5mV and Vin2 = +5mV
- Vin1 = -5mV and Vin2 = -5mV
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Observations:
(a) Comment on the results obtained when Vin1 = Vin2 = 0V. Is this what you would have expected?
(b) Comment on the results obtained when Vin1 > Vin2. Is this what you would have expected?
(c) Comment on the results obtained when Vin1 < Vin2. Is this what you would have expected?
(d) What can you say about the internal voltage gain of the operational amplifier?
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| Further work:
Obtain a set of manufacturers characteristics for a common type of operational amplifier. What value of voltage gain is specified by the manufacturer? (If this is specified in 'dB' convert the value to a ratio). Does this support what you have said in (d)?
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<^< Voltage Gain | Course index | Input Resistance >^>
