In the measurements of non-electrical physical quantities the most accurate result can often be obtained by indirect measurement using a nonelectrical to electrical transducer and amplifing the often very weak electrical signal, the transducer output. Since the electrical noise in devices such as resistor and transistor gives the limit of accuracy, it is important to suppress the noise as low as possible.
This called as low noise design and the design necessitates knowledge of the noise-mechanism and an adequate modeling of the noise sources. Modeling can be done by introducing two parameters, noise voltage $E_n$ and noise current $I_n$.
This thesis investigates the noise mechanism of resistors and transistors and the noise source has been modeled utilizing the above two parameters to obtain the noise data of the specific device, since noise data must be at hand prior to low noise design.
Since the two parameters $E_n$ and $I_n$ of low-noise transistors are of the order of $10^{-9}$V and $10^{-13}$A respectively, noise represented by these parameters has been evaluated by the following procedure. The original noise signal is amplified through an experimental low-noise and the resultant noise signal is applied to the Wave Analyzer to obtain the power spectrum of noise. This process has resulted in a maximum error of 10%.
The data evaluated by the above procedure and the characteristics of the given sensor have been used as the basis of the design of a low-noise amplifier. Finally, the measured value of noise of the designed amplifier has been compared with the theoretical value.
장션트랜지스터의 잡음을 측정하기 위해 테스터용 트랜지스터를 증폭기로 동작시키면 출력잡음전압은 수 백 nV정도가 되므로 다시 저잡음 전단 증폭기로 증폭시켜 Wave Analyzer에 가하여 주파수에 대한 잡음전압을 측정하고, 테스터회로의 입력에 정현파를 인가하여 전압이득을 구하여 이 값으로 잡음전압을 나누어서 입력 등가잡음을 구했다.
이 방법은 가청 주파수대의 여러종류의 잡음을 측정할 수 있을것이다. 위의 방법으로 측정한 트랜지스터의 잡음전압과 잡음전류 테이터부터 주어진 센서에 대한 저잡음 증폭기를 설계하고, 실제 회로를 구성하여 전 주파수 대역에 대한 잡음을 측정하였다.
