64. The PNP/NPN amplifier is used in place of ordinary direct-coupled amplifier in order to
A. achieve greater stability
B. avoid the problem of growing Vc's
C. amplify both dc and ac voltages
D. achieve greater amplification
65. Regarding differential amplifier which statement is wrong?
A. a single-stage amplifier has two inpute, one across each base
B. it has the ability to amplify the differnce between two signals
C. it is used to eliminate noise picked up along a short transmission line
D. it is not much used ICs
66. Cascaded amplifiers which find wide use in ICs are coupled.
67. An amplifier is used to amplify a 307c Hz square wave with a sag not exceeding 1%. Maximum permissible lower 3 dB frequency of the amplifier is___hertz.
68. The rise time of an amplifier is 200 ns. Its upper 3-dB frequency is
A. 70 MHz
B. 1.5 MHz
C. 1.75 MHz
D. 70 kHz
69. An electronic oscillator is
A. just like an alternator
B. nothing but an amplifier
C. an amplifier with feedback
D. a converter of ac to dc energy
70. The oscillator circuit that uses a tapped coil in the tuned circuit is
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