CRAC Class C (2025) — Questions 1011–1020
U1096. The three basic electrodes of a bipolar junction transistor are:
双极型三极管的三个基本电极是：
Exam tips · 考试提示
A 双极型三极管 (BJT) has 发射极/基极/集电极 (emitter/base/collector). The other sets belong to vacuum tubes, FETs, and SCRs respectively.
U1097. The three basic electrodes of a vacuum triode are:
电子三极管的三个基本电极是：
Exam tips · 考试提示
A 电子三极管 (vacuum triode) has 阴极/栅极/屏极(板极) (cathode/grid/plate-anode). Emitter/base/collector (B) are BJT; source/gate/drain (C) are FET; cathode/gate/anode (D) are SCR.
U1098. What is the minimum number of pins a vacuum triode must have?
电子三极管至少应有几个引脚？
Exam tips · 考试提示
A directly heated 电子三极管 uses its filament as the cathode, giving two filament pins plus the grid and plate — a minimum of 4 pins (A). An indirectly heated type needs a separate cathode and heater (5). Two or three pins cannot supply both the cathode function and the heater, so B/C are too few; D is a possible configuration but not the minimum.
U1099. The most commonly used parameter, unit, and symbol describing the amplification ability of a field-effect transistor are:
描述场效应晶体管放大能力的最常用参数、单位及符号是：
Exam tips · 考试提示
A FET's amplification is characterized by its 互导/跨导 (transconductance, gm), the ratio of drain-current change to gate-voltage change, in mA/V (or Siemens). β (B) is the BJT current gain; voltage gain is dimensionless but is not the defining FET parameter (C/D wrong units/symbols).
U1100. The most commonly used parameter, unit, and symbol describing the amplification capability of a bipolar transistor are:
描述双极型晶体管放大能力的最常用参数、单位及符号是：
Exam tips · 考试提示
For a bipolar junction transistor (BJT, 双极型晶体管), the standard figure of merit is the current gain (电流放大倍数), denoted β (or hFE), which is a ratio and therefore has no unit. Options B/C describe transconductance (gm), which characterizes a vacuum tube or FET, not a BJT; D describes voltage gain, which also is dimensionless but is not the primary BJT parameter.
U1101. The most commonly used parameter, unit, and symbol describing the amplification capability of an electronic triode (vacuum tube) are:
描述电子三极管放大能力的最常用参数、单位及符号是：
Exam tips · 考试提示
For an electronic triode / vacuum tube (电子三极管), the standard parameter is transconductance (互导/跨导), symbol gm, with unit milliampere per volt (mA/V). It expresses how much the plate current changes per volt of grid-voltage change. β (B) belongs to BJTs; C gives a wrong unit; D (voltage gain) is not the primary tube parameter.
U1102. If the control electrodes of devices are arranged in order of increasing input impedance, they could be:
若将器件上起控制作用的电极按输入阻抗由低到高排列，则可 以是：
Exam tips · 考试提示
Input impedance rises in the order: BJT base (current- controlled, lowest, needs base current) < JFET gate (reverse- biased PN junction, very high) < MOSFET/insulated-gate gate (isolated oxide, essentially infinite DC input impedance, highest). So A is the correct low-to-high sequence.
U1103. Which of the following components can be used to achieve the function of controlling a larger current with a smaller current? (Choose all that apply.)
下列哪种元器件可用来实现以较小的电流控制较大电流的功 能？
Exam tips · 考试提示
Both a transistor (晶体管) and a relay (继电器) provide current amplification / control: a small base/coil current controls a much larger collector/contact current. A resistor merely dissipates/limits current and a battery is a source, neither controls a larger current.
U1104. Which of the following components can be used both as an electronic switch and as an amplifier?
下列哪种元器件既可以用作电子开关又可以制成放大器来使 用？
Exam tips · 考试提示
A transistor (晶体管) operates in cut-off/saturation as a switch and in its linear region as an amplifier. A potentiometer is a passive divider, an SPDT switch is a mechanical contact, and a voltmeter is a measuring instrument — none amplifies.
U1105. An integrated circuit refers to:
集成电路是指：
Exam tips · 考试提示
An integrated circuit (集成电路) is defined as many circuit components fabricated together on a single semiconductor chip (单个晶片). B, C, D describe discrete or other assemblies, not integration on a chip.