Self-oscillation discrimination conditions
In electronic circuits, judging whether a circuit can produce self-oscillation has always been a problem that confuses students. When students analyze a circuit, they often feel that they cannot start. Based on years of teaching experience, a relatively simple method of identification is summarized. The details are as follows:
Usually, we can determine whether the circuit can produce self-oscillation can be from two aspects: one is the phase balance condition, and the other is the condition of amplitude balance. If any one of the two conditions is not satisfied, the circuit will not be brittle and generate self-oscillation. .
Under normal conditions, when we analyze the circuit, the first of these two conditions is the amplitude balance condition, which means that the feedback signal of the amplifier must have a certain amplitude. This condition contains two layers of meaning. First, there must be a feedback signal. Second, the anti-jamming signal must have a certain extent. In this way, we can consider two aspects when analyzing whether the circuit satisfies the conditions for the newspaper: (1) whether there is a feedback signal; (2) whether the triode can play a normal amplification. The following illustrates by way of example:
In the circuit shown in Figure 1, when considering the AC path, the feedback signal is short-circuited by the emitter capacitor Ce, and the feedback signal disappears. It does not satisfy the amplitude condition and cannot generate self-oscillation. In the circuits shown in Figure 2 and Figure 3, the DC path is considered and the inductor is considered as a wire. In Fig. 2, the coil short-circuits the smut electrode and the emitter. In Fig. 3, the coil short-circuits the collector and the base. Therefore, the triodes in both circuits cannot work normally, so the amplitude condition cannot be satisfied and the circuit cannot generate a self-report. swing.
If we know that the circuit satisfies the condition of the report by analyzing, then we look at the phase balance condition in the second step. It means that the feedback signal of the amplifier must be in phase with the input signal. In other words, the feedback loop in the circuit must be positive feedback. Regarding the discrimination of positive and negative feedback, we can use the "instantaneous polarity method". This group we also explain through a circuit.
In FIG. 4 , it is first assumed that the instantaneous polarity of the input signal voltage to ground is positive, and then the signal polarity fed back to the base can be seen from the corresponding signal polarities of the collector, base, and emitter of the instantaneous transistor. Sex is negative, it plays a role in weakening the input signal. It can be known as negative feedback. It does not satisfy the phase condition, so the circuit cannot generate self-oscillation.
From the above, it can be seen that a circuit that can generate self-oscillations must be a circuit that has both positive feedback and normal amplification. In other words, this circuit must satisfy both the amplitude condition and the phase condition to generate self-oscillation. Two conditions are indispensable.
Features
â—† Wide Application
Widely used for various kinds of electrical products, instrument, car, boat, household appliances such as lights, water dispenser, treadmill, coffee pot, speaker, electric car, motorcycle, TV, massage machine etc.
â—† Easy to install and use
3 PIN on-off Rocker Switch with SPST design, simple installation, freely turn on or off the load which you want to control.
â—† High Operating Life
Made of high quality polyamide eP(Nylon PA66) material, this sturdy mini boat rocker switch is born for anti-corrosion,anti-acid and high resistant with silver terminals.100,000 times of ON/OFF operating life span.
Round Rocker Switch,Power Rocker Switch,Black Rocker Switch,Sealed Rocker Switch
Ningbo Jialin Electronics Co.,Ltd , https://www.donghai-switch.com