The basics of the minimum amplification circuit for HI-FI home-made guns

Most HI-FI amateur enthusiasts enjoy welding and repairing machines. However, enthusiasm alone is not enough. You must have a certain foundation in electronic circuits. Only in this way can you achieve rational fever, rather than really burning the machine with smoke. Based on my own nearly 20 years of fever experience, I have summarized the minimum basic knowledge of amplifier circuits required for HI-FI fever. The detailed content still needs to be studied and understood in detail.
1. Common amplifier devices:
bipolar transistors (NPN, PNP), field effect tubes (junction field effect, insulated gate field effect, VMOS tube), composite tubes (Darlington tube, IGBT tube), operational amplifiers (voltage type, current type), integrated amplifiers, thick film circuits, and fool circuits.
2. Common materials for manufacturing semiconductors:
silicon (SI), germanium (GE), gallium (GA). The forward voltage drop of the PN junction made of silicon material is 0.6-0.7V, and the reverse withstand voltage can be more than 1000V. The forward voltage drop of the PN junction made of germanium material is 0.2-0.3V, and the reverse withstand voltage is generally within 100V. The reason why germanium cannot be widely used is that there is no way to overcome the problems of germanium's manufacturing process. The biggest problem is that the thermal stability is not good, so there is no way to apply it in large quantities.
3. Three working states of the triode:
The triode has three states in the circuit: cut-off, amplification, and saturation. In the amplification circuit, of course, we hope that the triode works in the amplification state. If it enters the saturation or cut-off state, saturation distortion or cut-off distortion (usually limiting distortion) may be generated. In addition, since the forward conduction of the PN junction is nonlinear, switching distortion and crossover distortion will be generated in the process from cut-off to amplification. The pure Class A power amplifier that everyone advocates now is to make the triode work in the amplification state all the time, thereby reducing various distortions.
4. Three configurations of amplifier circuits:
Common emitter configuration, the most widely used, the signal is input from the base and emitter, and output from the collector and emitter. It has higher input resistance, larger voltage and current magnification, wider frequency response, but the output resistance is relatively large.
Common base configuration, the signal is input from the emitter and base, and output from the collector and base. It has a wide frequency response and higher voltage and current magnification, but its input resistance is small and the output resistance is large.
Common collector configuration, the signal is input from the base and collector, and output from the emitter and collector. It has a very high input resistance, very low output resistance, and a very wide frequency response, but the voltage magnification is small (less than and close to 1) is the disadvantage of this configuration.
5. Single-ended amplification and push-pull amplification.
The output stage of the single-ended amplifier is completed by an amplifier element (or multiple elements but connected in parallel into a group) to amplify the positive and negative half cycles of the signal. Single-ended amplifiers can only take Class A working state.
The output stage of the push-pull amplifier has two "arms" (two groups of amplifier elements). When the current of one "arm" increases, the current of the other "arm" decreases, and the states of the two are switched in turn. For the load, it seems that one "arm" is pushing and the other "arm" is pulling, and they jointly complete the current output task. Although Class A amplifiers can use push-pull amplification, it is more common to use push-pull amplification to form Class B or Class A and Class B amplifiers.
6. Differential amplifier circuit.
Use two identical tubes to form two completely symmetrical circuits. Generally, they work in a common emitter configuration. The signal is input from the base of the two tubes and output from the collector. This is the most basic differential amplifier circuit; the differential amplifier circuit is used mainly to suppress the "zero drift" that may be generated by the circuit and improve the temperature characteristics of the amplifier circuit. There are
four basic connection methods for differential amplifier circuits: dual-end input and dual-end output, dual-end input and single-end output, single-end input and dual-end output, and single-end input and single-end output.
7. Typical applications of operational amplifiers:
We mainly use linear amplifier circuits of operational amplifiers. According to the connection form of the input signal, it can be divided into three situations:
reverse input, the circuit at this time has a certain depth of voltage parallel negative feedback. The circuit characteristics are: the input resistance is relatively small, the output resistance is very small, and the phase of the output signal is opposite to that of the input signal, and the common mode rejection ratio of the operational amplifier is not high.
In-phase input, the circuit at this time has a certain depth of voltage series negative feedback. The circuit characteristics are: the input resistance is relatively large, the output resistance is very small, the phase of the output signal is the same as that of the input signal, and the common mode rejection ratio of the operational amplifier is high.
Differential input (signals are input at the same time at the in-phase input and the inverting input), generally not widely used.
It is fun to play with circuits for amateurs. Why not improve your knowledge level by analyzing and improving the circuits?