1. The Difference Between AC Coupling and DC Coupling:
When using DC coupling, the actual signal being measured is directly displayed on the oscilloscope screen. This means that both the AC and DC components of the signal are visible. In contrast, when using AC coupling, the input signal passes through a capacitor before reaching the oscilloscope’s amplifier circuit. The capacitor blocks the DC component, allowing only the AC portion of the signal to be displayed. This is particularly useful when you want to observe only the varying part of the signal without the influence of any DC offset.
In terms of the matching circuit, DC coupling involves a direct connection between stages, often using resistors or other linear components. It is ideal for signals that contain DC components and require accurate representation across multiple stages. However, in DC-coupled circuits, the operating points of each stage are interdependent. A change in one stage can affect the next, making it difficult to adjust individual parameters independently.
On the other hand, AC coupling isolates each stage using capacitors or inductors, which prevents the DC bias from affecting adjacent stages. This allows for independent adjustment of the static operating points. Additionally, in AC-coupled systems, impedance matching is more flexible. Transformers or LC resonant circuits are commonly used to achieve efficient power transfer and better frequency response, especially in high-frequency or selective amplification applications.
2. What is AC Coupling (AC COUPLED)?
AC coupling is achieved by connecting a capacitor in series with the signal path. This setup allows only the AC component of the signal to pass through while blocking any DC voltage. While this has no effect on a pure AC signal (without DC), it effectively removes the DC component from a mixed signal. This behavior is due to the capacitor's ability to charge and discharge, which stabilizes the DC level over time.
After AC coupling, if you need to recover the original DC component, techniques like clamping or DC restoration are used. Clamping adds a specific DC reference to an AC signal, shifting its amplitude range to meet input or output requirements. For example, a signal ranging from 1–2V might be shifted to 4–5V to match the desired input level.
A common clamping method uses a diode such as BAV99, or two diodes connected in opposite directions to ground and a reference voltage. This configuration helps stabilize the signal’s voltage level. As shown in the diagram, the BAV99 ensures that the signal remains within a stable range, typically between -0.7V and +5.7V, depending on the circuit design.
Flat Cable
Flat Cable,Tpe Flat Data Cable,Usb Data Charging Cable,4-Core Usb Data Cable
ShenZhen Puchen Electronics Co., Ltd. , https://www.szpuchen.com