Current and voltage feedback judgment method

Do you know what a feedback circuit is? First of all, let's learn the basic points of negative feedback amplification circuit with everyone. What is negative feedback? Negative feedback is to ensure that our amplifier circuit can work normally within our operating range. The meaning of mining is that the feedback signal has the opposite phase to the input signal of our amplifier circuit and is subtracted.

What is positive feedback? The feedback signal of positive feedback has the same phase as our input signal. When adding, oscillation is actually very easy to occur at this time. Having said this, let's return to our topic. Let's first 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, there is no feedback signal, whether the sampling point and the output end are at the same point, if they are at the same point, it belongs to voltage feedback and the output end of the parallel circuit.

How to understand that the voltage feedback output resistance is small: it is beneficial for the parallel voltage to be equal everywhere and the parallel resistance becomes smaller. Summary: The sampling element of voltage feedback is a parallel output terminal with small output resistance.

We see that the output terminal here is fed back in parallel; it is concluded that it is voltage feedback. At the same time, the output signal is cancelled, and there is no signal in the feedback.

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

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

Let’s look at the picture: Let’s look at this, R is our load resistance.

Let's take a look. The RF sampling point and the output end are different points. They are connected in series to the sampling output resistor. When the output signal is cancelled, there is still a signal coming (see the endpoint is a negative signal). Summary: Look at the output end of the amplifier for voltage and current feedback. Voltage feedback reduces the output resistance, and current feedback increases the output resistance.

Voltage feedback can stabilize the output voltage, reduce output resistance, and improve load driving capabilities. Current feedback stabilizes the output current, increases the output resistance, and the load driving capability is not strong. The above is the method for judging current negative feedback. I hope many people will participate in the discussion.