Low frequency small signal amplification circuit

1. A lot of weak signals need to be amplified to facilitate processing, such as radio waves received by the radio antenna, the loudspeaker can not be driven without amplification, and the amplifier circuit is the most common type of circuit in the analog circuit.

The main focus of the small signal amplifier is that the amplitude of the input signal is relatively small, the main amplifier work in the linear state, emphasis on increasing the signal amplitude.

The so-called low frequency refers to the transistor and other active devices do not need to consider the capacitance effect, lines and components do not take into account the distribution of capacitor and  inductor.

In addition, the frequency range of low frequency has no absolute limit value, and generally refers to the frequency near the audio frequency ( 20Hz ~ 20kHz ). The core components of the amplifying circuit are transistors, field effect transistors and integrated amplifier circuits. They must have DC power when they work power supply, they can add the energy of the DC power to the signal, so as to realize the amplification of the signal.

2.Common emitter amplifier transistor

Common emitter amplifier circuit is one of the most common amplification circuits, which can amplify voltage, it can also amplify the current.

3. Common collector amplifier circuit

Common collector amplifier circuit is also known as emitter output.

The common collector amplification circuit is characterized in that the output signal and the input signal are in the same frequency as the same phase; can achieve current amplification, can not achieve voltage amplification; the input resistance is large, and the output resistance is small. It is often used in the input stage, the output stage or the middle isolation stage of the multistage amplifier, and is also an important basic circuit unit of the power amplifier.

4 Multistage amplifier circuit

 When the amplification of the first stage amplifier is not enough, we can consider the adoption of multi-stage amplifier circuit, the total voltage amplification of the multi-stage amplifier circuit a multiple equal to the product of voltage amplification at all levels. There are three main methods of connection between amplifier circuits : transformer coupling method, resistance-capacitance coupling method and direct coupling method. Because of the limitations of the transformer, the transformer coupling method is applied less and less in the low frequency, and is almost completely eliminated. Only the high-frequency field is still applied.

Direct coupling method is commonly used in integrated circuit design. The direct coupling design and debugging of discrete components are more complex. The circuit structure of the resistance-capacitance coupling method is clear, and each amplifier stage can be independently designed and debugged, and the application is the most extensive. The coupling capacitance is the core component of the resistance-capacitance coupling method. The size of the coupling capacitor can make the useful signal pass smoothly and avoid loss as far as possible.

If you want to know more, our website has product specifications for the amplifiers, you can go to ALLICDATA ELECTRONICS LIMITED to get more information