CRAC Class C (2025) — Questions 1021–1030

U1106. The basic concept of an ideal operational amplifier is: (Choose all that apply.)

理想运算放大器的基本概念是：

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An ideal op-amp (理想运算放大器) has infinite open-loop gain (A) and infinite input impedance with both inverting (−) and non-inverting (+) inputs (B). C and D wrongly equate "ideal" with a specific transistor type or unlimited output swing; the ideal model is about gain/impedance, not device technology.

U1107. What type of integrated circuit does an integrated operational amplifier belong to?

集成运算放大器属于什么类型的集成电路？

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An integrated operational amplifier (集成运算放大器) processes continuous analog signals, so it is an analog integrated circuit (模拟集成电路). MMIC (B) is for RF/microwave; digital ICs (C) and PLDs (D) handle logic, not linear amplification.

U1108. Some integrated circuits commonly seen in amateur radio projects, such as operational amplifiers and microprocessors, sometimes have letter suffixes added after the marked model number, e.g., SIP, DIP, SOT, SOP, SSOP, QFP, etc. They are used to indicate:

业余无线电作品中常见的一些集成电路，例如运算放大器和微处理器等，有时会在所标型号之后附加字母尾缀，例如SIP、 DIP、SOT、SOP、SSOP、QFP等。它们用来说明：

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Suffixes such as DIP (dual in-line package), SOP/SSOP (small- outline package), QFP (quad flat package), SIP (single in-line), SOT (small-outline transistor) denote the physical package form (封装形式) of the IC, not temperature, logic levels, or frequency. 晶体管放大电路 Transistor Amplifier Circuits

U1193. The circuit shown in the figure is:

图中的电路为：

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The figure (LK0734.jpg) shows the input applied to the emitter and the output taken from the collector with the base AC- grounded (biasing network) — i.e. the 共基极放大器 (common- base amplifier), where the base is the common terminal. A is correct; common-gate is the FET counterpart in D.

U1194. In the transistor amplifier circuit below, the common name and function of Rc is:

在下面的三极管放大电路中，Rc的常用名称和作用是：

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In a common-emitter stage, Rc (collector resistor) is the 负载电阻 (load resistor): the varying collector current develops the output signal voltage across it (Vout = Vcc − Ic·Rc). A is correct; Re is the emitter feedback resistor, Rb the bias resistor.

U1195. In the transistor amplifier circuit below, the common name and function of Re is:

在下面的三极管放大电路中，Re的常用名称和作用是：

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Re is the 发射极负反馈电阻 (emitter resistor); the DC voltage drop across it provides negative feedback that stabilizes the operating (quiescent) point against temperature/β variations. A is correct; Rb is the bias resistor.

U1196. In the transistor amplifier circuit below, the common name and function of Rb1 is:

在下面的三极管放大电路中，Rb1的常用名称和作用是：

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Rb1 is the upper 偏流电阻 (bias resistor) of the base divider; it sets the base bias current/voltage that establishes the operating point. A is correct; Rc is the load and Re is the emitter feedback.

U1197. In the transistor amplifier circuit below, the common name and function of Cb is:

在下面的三极管放大电路中，Cb的常用名称和作用是：

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Cb at the input is the 输入耦合电容 (input coupling/DC-blocking capacitor): it passes the AC signal into the base while blocking DC bias from the preceding stage. A is correct; Cc is the output coupler and Ce the emitter bypass.

U1198. In the transistor amplifier circuit below, the common name and function of Ce is:

在下面的三极管放大电路中，Ce的常用名称和作用是：

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Ce is the 旁路电容 (emitter bypass capacitor) across Re: at AC it shorts the emitter to ground so Re does not degenerate (reduce) the gain, while DC still sees Re for bias stability. A is correct.

U1199. In the transistor amplifier circuit below, the common name and function of Cc is:

在下面的三极管放大电路中，Cc的常用名称和作用是：

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Cc at the output is the 输出耦合电容 (output coupling/DC- blocking capacitor): it transmits the amplified AC to the next stage while blocking the collector's DC bias. A is correct; Cb is the input coupler.