1、 I 调调频调幅接收机频调幅接收机毕业论文毕业论文 摘摘 要要 收音机的发展一般经过电子管、晶体管再到集成电路。集成电路收音机由于使用 元器件少、可靠性强、耗电省、成本低、重量轻、体积小等优点，已经开始取代分立 元件式晶体管收音机。此接收机采用的就是单片调频调幅集成电路ULN2204。UNL2204 集成电路有以下几个特点：其内部几乎包括了收音机所必需的电路，有独立的调幅振 荡器、调幅双平衡混频器、调幅和调频中频放大器、调幅和调频解调器、AGC电路、 AFC电路和功率放大器等。为使外接元件少且便于集成，ULN2204内部大量采用直接耦 合的电路形成；工作电压范围宽。UNL2204内部设有精密稳
2、压电路，而且外加电源电 压的范围大，其允许变动的范围为312V；用集成双差分放大电路组成混频器，提高 了对信号中干扰成分的抑制能力；灵敏度高。具有5级中频放大，级间均采用直接耦 合。前4级可以加AGC控制；外接元件少。中频放大直接耦合，无需外接元件。整个功 率放大部分只接1只退耦电容；功率放大器的输入阻抗高，约为200千欧姆；调幅收音 机与调频收音机的转换十分简单，仅用1只2*2波段开关，控制UNL2204内部的电子开 关，完成调幅收音与调频收音的转换。此调频调幅接收机的电源供给采用自带直流稳 压电源直接供给。 II FM-AM Receiver Abstract The developmen
3、t of general over the radio tubes, transistors to integrated circuits. IC Radio as the use of fewer components, reliability, low power consumption, low cost, light weight, small size, etc., has begun to replace discrete transistor radio. This receiver is used in single-chip FM-AM IC ULN2204. UNL2204
4、 IC has the following characteristics: its internal includes almost necessary for the radio circuit, independent amplitude modulation oscillator, amplitude modulation double-balanced mixer, IF amplifier AM and FM, AM and FM demodulator, AGG circuit, AFC circuit and power amplifier. To enable small and easy to integrate external components, ULN2204 house a large number of direct-coupled circuit formation; wide operating voltage range. UNL2204 are equipped with sophisticated internal regulato
