First of all, PCB mill will learn the basic points of the negative feedback amplifier circuit with everyone.
What is positive feedback, the phase of the feedback signal of positive feedback is the same as that of our input signal, and when adding, it is actually easy to appear oscillation 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 phase of the feedback signal is opposite to that of the input signal of our amplifying circuit, and subtraction is done.
Having said that, let's go back to our topic, let's take a look at what voltage feedback is.
Voltage feedback takes out the voltage of the output signal from the output terminal of the amplifier in order to stabilize the voltage of the output signal.
Voltage feedback judgment: the output signal is cancelled, the feedback has no 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 beneficial to understand that the parallel voltage is equal everywhere, and the parallel resistance becomes smaller.
Summary of the circuit board factory: the sampling element of the voltage feedback is a parallel output terminal, and the output resistance is small.
We see that the output terminal here is fed back in parallel; it is judged to be voltage feedback, and the output signal is canceled at the same time, and the feedback has no signal. After reading what is voltage feedback, 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 is that the feedback elements are connected in series. output of our feedback. Increase the resistance value of the output resistor. At the same time the feedback sampled signal is not at the same endpoint as our output.
Look at the picture and talk: Let's look at this, R is our load resistance.
PCB factory will take a look with you. The sampling point of RF is different from the output terminal. It is connected in series with the sampling output resistor. When the output signal is canceled, there is still a signal coming (see the terminal is a negative signal).
Circuit board factory summary: voltage and current feedback depends on the output terminal of the amplifier, voltage feedback reduces the output resistance, and current feedback increases the output resistance.
Voltage feedback can stabilize the output voltage, reduce the output resistance, and improve the ability to drive the load.
