[A+] 중앙대학교 전자회로 설계실습 결과보고서 7. Common Emitter Amplifier의 주파수 특성

본 내용은 " [A+] 중앙대학교 전자회로 설계실습 결과보고서 7. Common Emitter Amplifier의 주파수 특성 " 의 원문 자료에서 일부 인용된 것입니다. 2023.02.09

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• 1. Common Emitter Amplifier

  본 실험에서는 Common emitter amplifer의 주파수 특성을 측정하였다. 첫 번째 실험에서는 설계실습 06에서 2차 설계를 완료한 common emitter amplifer를 구현하고, Bias를 측정하였다. Bias가 PSPICE의 결과와 오차율 1% 정도의 정확한 값을 보였지만, 는 13.3%의 큰 오차율을 보였고, 이는 [㎂]라는 매우 작은 단위 때문이라 생각하였다. 는 에 의존하므로 동일하게 큰 오차율을 보였다. max min는 2차 설계를 통해 을 연결하여 95%의 값을 기대하였지만, 86.1%라는 결과가 나왔고, PSPICE의 이상적인 결과와 달리 BJT의 non-linear 특성을 비롯한 여러 오차 요인으로 인한 결과라고 판단하였다. 두 번째 실험은 2차 설계 Common emitter amplifer와 , 값을 변경시킨 회로의 주파수 특성을 측정하였다.

• 2. Frequency Response

  2차 설계 common emitter amplifier의 Bandwidth는 PSPICE의 경우 355 [kHz], 실험 결과 300 [kHz]이다. 를 0.1 [㎌]로 교체한 amp의 Bandwidth는 PSPICE의 경우 482 [kHz], 실험 결과 350 [kHz]이다. 두 개의 를 0.1 [㎌]로 교체한 amp의 Bandwidth는 PSPICE의 경우 462 [kHz], 실험 결과 450 [kHz]이다. Gain이 최대인 주파수의 값 자체는 PSPICE 시뮬레이션과 실험결과가 큰 차이를 보이지만 경향이 매우 비슷하다는 것을 확인할 수 있었다. 이는 Sedra Smith의 Microelectronic circuits에서 CE amplifier with an emitter resistance의 low cut-off frequency 수식을 통해 확인할 수 있다.

• 3. Bypass Capacitor

  저주파에서는 있다. 와 같은 bypass capacitor에 의해 gain의 값이 감소하고, 고주파에서는transistor internal capacitor에 의해 gain의 값이 감소하는 것을 그래프를 통해 확인할 수 있다.

• 4. BJT Characteristics

  BJT의입출력관계식이 이므로 전압이 exponential 함수이다. 이러한 영향을 최소화시키 이상적인 결과기 위해 지난 실습에서 2차 설계를 통해 을 연결하였지만, 어서 86.1%라는 값이 나왔다고 생각한다.를 보여주는 PSPICE와 달리 실제 실험에서는 저항값을 비롯한 다양한 오차 요소가 있 Gain은 출력이 입력과 닮은 꼴일 때에만 의미를 갖는데, 본 실험과 같이 입력전압이 작을 경우 noise와 더불어 출력 파형이 왜곡(distortion) 되므로 gain의 의미가 없어져 서 amplfier gain의 오차율은 분석하지 않았다.

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• 1. Common Emitter Amplifier

  The common emitter amplifier is a fundamental transistor amplifier configuration that is widely used in electronic circuits. It provides a good balance of voltage gain, current gain, and input/output impedance characteristics, making it a versatile and practical choice for many applications. The common emitter amplifier utilizes the transistor's ability to control a large output current with a small input current, allowing it to effectively amplify signals. Its simplicity, stability, and ease of biasing make it a popular choice for analog circuit design. While other amplifier configurations like the common base and common collector have their own advantages, the common emitter remains a workhorse of analog electronics due to its overall performance and flexibility.

• 2. Frequency Response

  Frequency response is a critical parameter in the design and analysis of electronic circuits, as it determines how a circuit will behave across different frequencies. Understanding the frequency response of a circuit is essential for ensuring proper operation, optimizing performance, and avoiding unwanted effects like distortion or instability. A good frequency response is characterized by a wide bandwidth, flat gain across the desired frequency range, and a smooth transition between the passband and stopband. Factors like component values, circuit topology, and feedback mechanisms all influence the frequency response. Careful analysis and design techniques are required to achieve the desired frequency response characteristics, whether for amplifiers, filters, or other signal processing circuits. The ability to accurately predict and control the frequency response is a key skill in analog and mixed-signal circuit design.

• 3. Bypass Capacitor

  Bypass capacitors are a fundamental component in electronic circuit design, serving a crucial role in maintaining signal integrity and power supply stability. These capacitors are used to provide a low-impedance path for high-frequency signals, effectively bypassing the higher impedance of other circuit elements like resistors or inductors. This helps to decouple different sections of a circuit, preventing unwanted coupling, noise, and oscillations. Bypass capacitors are particularly important in power supply circuits, where they help to filter out high-frequency ripple and noise, ensuring a clean and stable voltage supply for sensitive analog and digital components. The selection of the appropriate bypass capacitor value and placement is critical, as it can impact the overall performance and stability of the circuit. Proper bypass capacitor design is a key consideration in both analog and digital circuit design, and is essential for achieving reliable and high-performance electronic systems.

• 4. BJT Characteristics

  Bipolar junction transistors (BJTs) are fundamental building blocks of analog and mixed-signal electronic circuits, and a deep understanding of their characteristics is essential for effective circuit design. BJTs exhibit a range of important characteristics, including current gain, input/output impedance, frequency response, and nonlinear behavior, all of which must be carefully considered when using them in amplifiers, switches, oscillators, and other applications. The ability to accurately model and predict BJT characteristics is crucial, as it allows designers to optimize circuit performance, minimize distortion, and ensure stable operation. This requires a thorough understanding of the underlying physics and operating principles of BJTs, as well as the ability to apply appropriate analysis techniques, such as small-signal and large-signal models. Mastering BJT characteristics is a fundamental skill for any electronics engineer, as it underpins the design of a wide range of analog and mixed-signal circuits that are essential in modern electronic systems.