3.1
Amplificateurs opérationnels
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Q1: What is an operational amplifier and what does it do?
An operational amplifier, or op-amp, is an electronic component that functions as a voltage-controlled voltage source. It amplifies weak signals to activate systems like fire alarms and performs mathematical operations including summing, integrating, and differentiating signals when external components like resistors and capacitors are connected to its terminals.
Q2: How many pins does a typical operational amplifier have?
A typical op-amp in an eight-pin dual in-line package has eight pins: two input pins (inverting and non-inverting), one output pin, two power supply pins, and three additional pins for offset null or balance. The five significant terminals are the inverting input, non-inverting input, output, positive power supply, and negative power supply.
Q3: What is the difference between inverting and non-inverting inputs?
An input applied to the non-inverting input appears with the same polarity at the output, while an input applied to the inverting input appears inverted at the output. The circuit symbol marks the inverting input with a minus sign and the non-inverting input with a plus sign to distinguish their opposite effects.
Q4: Why do operational amplifiers require power supplies?
As an active component, an op-amp requires voltage supplies to function. The current drawn from power supplies is the sum of the output current and the current needed to power the amplifier's internal circuitry, which consists of a complex network of resistors, transistors, capacitors, and diodes.
Q5: What are common integrated circuit packages for operational amplifiers?
Operational amplifiers are commercially available in various integrated circuit packages. One of the most common is the LM741, sold in an eight-pin dual in-line package. These packages make op-amps popular in practical circuit designs due to their adaptability, affordability, and ease of use.
Q6: How does an op-amp amplify signals in a fire alarm system?
In a temperature detector fire alarm system, a thermistor sensor initiates a small current flow during a fire. This signal is too weak to trigger the alarm system directly, so an operational amplifier amplifies the signals to activate the alarm. The op-amp strengthens the weak sensor signal to a level sufficient for system activation.
Q7: What mathematical operations can an operational amplifier perform?
An operational amplifier can perform a broad range of signal-processing operations including summing signals, amplifying signals, integrating, and differentiating. These capabilities are achieved by connecting external components like resistors and capacitors to the op-amp's terminals, enabling it to execute mathematical operations.