The operational amplifier is a circuit unit with a very high amplification factor. In actual circuits, a certain functional module is usually combined with a feedback network. It is an amplifier with a special coupling circuit and feedback. At present, operational amplifiers are widely used in the electronics industry, but if some rules are not "observed" during the use of operational amplifiers, serious consequences may result. Let's talk about a little experience and experience of operational amplifiers.

1. The output voltage of the operational amplifier

Operational amplifiers currently on the market still have some unavoidable defects, and the output voltage is difficult to reach its ideal power supply voltage (the power supply voltage can be reached under no-load conditions). And in practical applications, the output voltage will have a certain load, the greater the load, the greater the voltage loss. At this time, if a negative power supply is introduced, its voltage output can reach the ideal power supply voltage range.

2. Do not connect capacitors in parallel to the feedback loop of the operational amplifier

If a circuit used for DC signal amplification is accidentally connected to the feedback loop with a capacitor for decoupling, the phase of the feedback signal changes, and it is easy to oscillate. Therefore, in the amplifying circuit, the feedback loop cannot add any circuit that affects the phase of the signal.

3. Layout considerations for feedback loop

The components of the feedback loop must be close to the operational amplifier, and the PCB traces should be as short as possible, while avoiding interference sources such as digital signals and crystal oscillators as much as possible. If the layout of the feedback loop is unreasonable, it will easily introduce noise, which will seriously cause self-oscillation.

4. Operational amplifier input voltage limit

As we all know, electronic components work normally within a specific input voltage range, and operational amplifiers are of course no exception. If the input voltage of the operational amplifier exceeds the range, the operational amplifier will not work properly, or even some more serious conditions.

5. The use of operational amplifiers must pay attention to power supply filtering

The power supply filtering of the operational amplifier cannot be ignored, and the quality of the power supply directly affects the output. Especially for high-speed operational amplifiers, the power supply ripple has a great interference to the output of the operational amplifier, and it will become a self-oscillation if it is damaged. So the best operational amplifier filter is to add a 0.1uF decoupling capacitor and a tens of uF tantalum capacitor next to the power pin of the operational amplifier, or connect a small inductor or magnetic beads in series, the effect will be better.