| 摘要 |
PURPOSE:To reduce the power consumption of a frequency demodulation circuit by providing a current source to the collector terminal of a transistor with a resistance set between the transistor collector and the ground to increase the working speed of the transistor and improve the frequency characteristics of the frequency demodulation circuit. CONSTITUTION:A constant current source 32 is provided to a transistor (TR)13a. When the TR13a is turned off, a parasitic capacity 22 is charged quickly by the source 32. Thus the collector potential of the TR13a is set instantaneously at 'H'. A resistance 31 set between the collector terminal of the TR13a and the ground serves as a current path of the source 32 when the TR13a is turned off. Then the level of a signal G can be changed at a time point 'H' with control of the resistance value of the resistance 31. While the collector potential of the TR13a is reduced down to 0 when the TR13a is turned on. Thus the current of the source 32 flows only to the TR13a and not to the resistance 31.
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