单项选择题
Operational amplifiers, used primarily in analog circuits, are characterized by（）
A.high input impedance, high gain and low output impedance
B.high input impedance, high gain and high output impedance
C.low input impedance, low gain and high output impedance
D.low input impedance, high gain and low output impedance
相关考题
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单项选择题
CFC refrigerants exposed to high temperature or direct flame, will decompose and may produce（）
A.methyl chloride
B.ammonia
C.hydrofluoric acid
D.ozone -
单项选择题
The major difference between the discharge and suction valves installed in most low pressure, reciprocating air compressors is that（）
A.one valve seats upwards, while the other seats downwards
B.the reed valves used on the discharge are made substantially thicker and heavier than the suction valves
C.the suction valve springs exert a greater tension than the discharge valve springs
D.the discharge valve springs exert a greater tension than the suction valve springs -
单项选择题
Which of the following problems will occur if the internal drain at either end of a hydraulic, two-way, spool-type directional control valve cylinder were to become plugged?（）
A.The reservoir would become vapor bound
B.The valve would be placed in hydraulic lock
C.The spring loaded relief ports would open
D.The buffering chambers would be unable to function
