PCB Tech - Circuit board factory: analysis of key points of current and voltage feedback judgment

Circuit board factory: analysis of key points of current and voltage feedback judgment

First of all,the circuit board factory will first learn the basic points of the negative feedback amplifier circuit with everyone.

What is positive feedback? The phase of the feedback signal of the positive feedback is the same as our input signal. If the addition is done, it is actually easy to appear oscillations at this time.

What is negative feedback? Negative feedback is to ensure that our amplifying circuit can work normally within our operating range. The meaning of mining is that the feedback signal is opposite to the input signal of our amplifying circuit and is subtracted.

Having said this, let’s return to our topic, let’s take a look at what voltage feedback is.

The voltage feedback takes the voltage of the output signal from the output of the amplifier to stabilize the voltage of the output signal.

Voltage feedback judgment: the output signal is cancelled, there is no feedback signal, whether the sampling point and the output terminal are at the same point, if it is a point, it belongs to the voltage feedback, and the output terminal of the parallel circuit.

How to understand that the voltage feedback output resistance is small: It is helpful to understand that the parallel voltage is equal everywhere, and the parallel resistance becomes smaller.

The circuit board factory summarizes: The sampling element of voltage feedback is parallel output, and the output resistance is small.

We see that the output terminal here is feedback in parallel; it is determined that it is voltage feedback, and the output signal is cancelled at the same time, and there is no feedback signal.

After reading what voltage feedback is, let’s take a look at current feedback.

Current feedback: It is to collect the current of the signal at the output of our amplifier. We know that the current of the series resistance is equal everywhere, and the series resistance is equal to the sum of each resistance. We can use this to understand that the current feedback means that the feedback element is connected in series. The output terminal of our feedback. Increase the resistance of the output resistor. At the same time, the feedback sampled signal is not at the same end as our output terminal.

Look at the picture and talk: Let's look at this, R is our load resistance.

The circuit board factory and everyone looked at it. The sampling point and the output end of the RF are different points. They are connected in series with the sampling output resistance. When the output signal is cancelled, there is a signal coming (see the end point is a negative signal).

The circuit board factory summarizes: Voltage and current feedback look at the output of the amplifier. Voltage feedback reduces output resistance, and current feedback increases output resistance.

Voltage feedback can stabilize the output voltage, reduce output resistance, and improve the ability to drive loads.