Title:
【発明の名称】定電流回路および発振回路
Document Type and Number:
Japanese Patent JP2763393
Kind Code:
B2
Abstract:
An oscillating circuit (5, 6, 7) whose oscillation frequency can be varied with change of a constant current circuit output current I2, which in turn can be varied with change of a power source voltage Vcc, suitable for use in portable computers. A suitable constant current circuit (1, 2, 3, 4) comprises bipolar transistors (Q3, Q5) coupled to form a differential amplifier (3) wherein one of the transistors (Q3) is supplied with a reference voltage (V1) and the other (Q5) is supplied with a divided voltage of the power source voltage Vcc, and a resistor (R4) connecting the emitters of the transistors is provided for controlling the slope of the Vcc-I2 characteristic curve of the constant current circuit. The oscillating circuit comprises a capacitor (Co) charged by current I2, a switching means (SW) for discharging the capacitor when closed, and a voltage detecting means (D1) operating to close or open the switching means (SW) according to the voltage at one end of the capacitor (Co). Thus, the switching means switches on and off to generate pulses with a frequency depending on I2, hence, depending on Vcc. Methods for controlling the frequency range of the oscillating circuit and the rise time to fall time ratio of the pulses by introducing additional constant current supplying sources are also disclosed.
Inventors:
SUWADA MAKOTO
INOE SHUICHI
USUI JUZO
INOE SHUICHI
USUI JUZO
Application Number:
JP25629490A
Publication Date:
June 11, 1998
Filing Date:
September 26, 1990
Export Citation:
Assignee:
FUJITSU KK
International Classes:
G05F1/56; G05F3/22; G05F3/26; H03F3/343; H03K3/0231; H03K4/50; H03K4/502; (IPC1-7): G05F1/56; H03K4/50
Attorney, Agent or Firm:
Fumihiro Hasegawa (2 outside)