Difference between revisions of "Operational Amplifiers (Op-Amps)"
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Op-amps and transistors are the staples of analog circuit design. Internally, op-amps consist of many transistors, capacitors, and resistors |
Op-amps and transistors are the staples of analog circuit design. Internally, op-amps consist of many transistors, capacitors, and resistors; all crammed onto a small integrated circuit. |
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The symbol for an op-amp:[[Image:op_amp_symbol.gif]] |
The symbol for an op-amp:[[Image:op_amp_symbol.gif]] |
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Each op-amp has an inverting input, a non-inverting input, and an output. In practice, op-amps also must be powered and |
Each op-amp has an inverting input, a non-inverting input, and an output. In practice, op-amps also must be powered by a positive and negative voltage, but since the power and ground won't affect our schematic design, the leads are usually omitted in the drawings. |
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==Ideal Op-Amps== |
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Op-amps are generally very well described the their ideal model.There are several basic rules for ideal op-amps: |
Op-amps are generally very well described the their ideal model.There are several basic rules for ideal op-amps: |
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1. There is no voltage difference across the inputs. Although the gain of an ideal op-amp is considered to be infinitely large, the op-amp will try to keep the inputs at the same voltage |
1. There is no voltage difference across the inputs. Although the open-loop gain of an ideal op-amp is considered to be infinitely large, the op-amp will try to keep the inputs at the same voltage if it can somehow send the output signal back to the input to push or pull the input voltages to the same level. |
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2. The input current draw is zero. In real op-amps, there will be a small current draw because the op-amp does not have infinite resistance (maybe <math>10^12\Omega</math> for FETs and <math>10^8\Omega</math> for BJTs). |
2. The input current draw is zero. In real op-amps, there will be a small current draw because the op-amp does not have infinite resistance (maybe <math>10^12\Omega</math> for FETs and <math>10^8\Omega</math> for BJTs). |
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3. The output impedance is zero. This means that the output current does not affect the output voltage. |
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==The 741 and 411 Type Op-Amps== |
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The 741 (bipolar) and 411 (FET) families of op-amps are popular chips made by many manufacturers. The model number is often preceded by a modifier/identifier, such as "LM741" or "LF411". |
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[[Media:LM471.pdf]] |
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Revision as of 11:59, 23 June 2006
Op-amps and transistors are the staples of analog circuit design. Internally, op-amps consist of many transistors, capacitors, and resistors; all crammed onto a small integrated circuit.
The symbol for an op-amp:
Each op-amp has an inverting input, a non-inverting input, and an output. In practice, op-amps also must be powered by a positive and negative voltage, but since the power and ground won't affect our schematic design, the leads are usually omitted in the drawings.
Ideal Op-Amps
Op-amps are generally very well described the their ideal model.There are several basic rules for ideal op-amps:
1. There is no voltage difference across the inputs. Although the open-loop gain of an ideal op-amp is considered to be infinitely large, the op-amp will try to keep the inputs at the same voltage if it can somehow send the output signal back to the input to push or pull the input voltages to the same level.
2. The input current draw is zero. In real op-amps, there will be a small current draw because the op-amp does not have infinite resistance (maybe for FETs and for BJTs).
3. The output impedance is zero. This means that the output current does not affect the output voltage.
The 741 and 411 Type Op-Amps
The 741 (bipolar) and 411 (FET) families of op-amps are popular chips made by many manufacturers. The model number is often preceded by a modifier/identifier, such as "LM741" or "LF411". Media:LM471.pdf
