In the final paper titled Basic amplifier assemblies with bipolar transistor I wrote about the basic characteristics of a bipolar transistor. I have described the transistor structure in pn and np fusion. He showed how the transistor behaves in the active working area, that it is executed discreetly and that it is an integrated circuit. Below I described the transistor in a joint base. What happens to the input characteristics, what function they have the voltage and current of the emitter, collector and base. In the output characteristics of the common base connection I showed the output output current dependency on the output voltage when using the input current as a parameter. The area of normal active and saturation area is located in the first and second quadrants while their bounds represent positive current. The field of zaping is aligned with a positive absent since 𝑈𝐶𝐵 > 0 𝑖 𝑈𝐸𝐵 > 0. The amplifier in the common ground current converter does not have a value greater than 1. The current of the emitter that is the input current is always for the amount of base current greater than the output current or collector current when operating in the normal active range. This transistor connection provides significant voltage boost. The ability to work on a common basis increases the voltage signal to ensure a different dynamic input and output circuit resistance. In the input characteristics, in the emitter of the emitter the current of the emitter is the current of the ground electrode which does not appear either at the input or at the output of the transistor. The characteristics show the dependence of the input base 𝐼𝐵 on the input voltage 𝑈𝐵𝐸 with the output voltage 𝑈𝐶𝐸 as a parameter. In the normal active area we have 𝑈𝐵𝐸 > 0, 𝑈𝐶𝐸 > 0, 𝑈𝐶𝐸 > 𝑈𝐵𝐸 . The input characteristics of the transistor in the common emitter circuit break in the normal active area into a curve independent of the 𝑈𝐶𝐸 when it is greater than 𝑈𝐵𝐸 . The bipolar transistor in the joint of the common emitter in the normal active area possesses a significant current amplification. We use the relay for the alternating current signal assuming that the transistor works in the part of the small signal. The ℎ𝑓𝑒 factor is mostly greater than 1 and generally of the order of 100. We need to keep an eye on the power amplifier that it receives the power signal from the generator at the input and amplifies it to the consumer at the output of the amplifier. For amplifiers in a common collector circuit, what differs from a common emitter is that the consumer is located in the emitter circuit, and the collector is connected directly to the collector battery, thereby grounding the acoustic signal. The resistor function 𝑅1 𝑎𝑛𝑑 𝑅2 is the same as the amplifier in a common emitter and common base.