The capacitive reactance of a capacitor is related to frequency. The higher the frequency, the lower the capacitive reactance, which is equivalent to a small resistance. So for high-frequency current, the capacitive reactance of the capacitor is very small, which is equivalent to a branch with very small resistance, so the high-frequency current is short-circuited here and cannot reach the input of the subsequent stage. On the contrary, for low-frequency current, the capacitive capacitance is large, so it will not be short-circuited and can reach the output of the subsequent stage.
In electronic instruments, the alternating current output from a device often has high-frequency components and low-frequency components. At this time, the high-frequency bypass capacitor can filter the high frequency (let the high frequency pass through the branch where the high-frequency bypass capacitor is located) to retain the low frequency (low frequency output). The capacitor that plays this role is called high frequency Bypass capacitor.
Capacitors that pass high frequencies and block low frequencies have a small capacitive reactance to high frequency components and a large capacitive reactance to low frequency components, and the high frequency components pass through the capacitors, so that the low frequency components are delivered to the next stage. Capacitors for this purpose are called high-frequency bypass capacitors. The capacitance of high-frequency bypass capacitors is generally small.
In electronic technology, if you want to remove the DC component from the output signal of the previous stage, as long as the AC component is sent to the next stage, we can connect a capacitor in series between the circuit of the front and back stage. “DC” characteristics, such a capacitor is called a DC blocking capacitor.
If you want to keep the low-frequency components in the previous stage and remove the high-frequency components, you can connect a capacitor in parallel with the input of the next-stage circuit. Then the high-frequency components pass the capacitor, and the low-frequency components show a large impedance and cannot pass. Go to the next circuit. This is the use of the characteristics of the capacitor “pass high frequency, block low frequency”, such a capacitor is called a high frequency bypass capacitor.