Low noise amplifier features

- May 03, 2016-


Low noise amplifier, low noise figure amplifier. It is generally used as a high frequency or intermediate frequency preamplifier for various types of radio receivers, as well as an amplifying circuit for high sensitivity electronic detection equipment. In the case of amplifying a weak signal, the noise of the amplifier itself may be severely disturbed by the signal, so it is desirable to reduce this noise to improve the signal-to-noise ratio of the output.

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An amplifier with a very low noise figure. It is generally used as a high frequency or intermediate frequency preamplifier for various types of radio receivers, as well as an amplifying circuit for high sensitivity electronic detection equipment. In the case of amplifying a weak signal, the noise of the amplifier itself may be severely disturbed by the signal, so it is desirable to reduce this noise to improve the signal-to-noise ratio of the output. The degree of deterioration of the signal-to-noise ratio caused by the amplifier is usually expressed by the noise figure F. The noise figure of an ideal amplifier is F = 1 (0 dB), and its physical meaning is that the input signal-to-noise ratio is equal to the output signal-to-noise ratio. Modern low-noise amplifiers mostly use transistors and field-effect transistors; microwave low-noise amplifiers use varactor-parameter amplifiers, the noise temperature Te of normal temperature can be lower than tens of degrees (absolute temperature), and the cooling parametric amplifier can reach 20K. In the following, GaAs field effect transistor low noise microwave amplifiers have been increasingly used with noise figures below 2 dB. The noise figure of the amplifier is also related to the operating state of the transistor and the internal resistance of the source. In order to balance the requirements of low noise and high gain, a low noise amplifying circuit with a common emitter and a common base is often used.


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