1. A commonly used passive low-pass filter circuit
The low-pass filter circuit shown in the diagram above, composed of RC circuits, is very common and frequently appears in DC signal processing. Those familiar with RC calculus circuits will recognize it as an RC integrator circuit; in fact, integrator circuits also function as low-pass filters.
The voltage acquisition circuit shown in the figure below uses this filter circuit.
2. Zener diode voltage regulator circuit
It seems simple, consisting of just a resistor and a Zener diode, but it's not easy for beginners. You can't just randomly choose a diode that meets the voltage regulation requirements and pair it with a resistor. What's the appropriate value for the resistor R? This needs to be matched based on the Zener diode's normal operating current range and the voltage load.
It's best to understand the I/O curve of the Zener diode and the entire voltage regulation process.
3. Voltage comparator circuit
As shown in the diagram above, the voltage comparator works like this: when V1 > V2, the output is low (GND).
4. Operational amplifier circuit
The diagram above shows the principle of a non-inverting operational amplifier circuit. The output formula is: VO = VI × (1 + R2/R1)
The above diagram illustrates the principle of an inverting input op-amp. The output formula is: VO = -VI × (R2/R1).
You need to learn to use the principles of "virtual open" and "virtual short" at the positive and negative input terminals of the op-amp to make calculations.
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