| 摘要 |
PURPOSE:To stabilize a constant current and a rise time and a breaking time by providing an electronic switch for a base terminal of a constant current source circuit. CONSTITUTION:In constant current source circuits 20' and 30' of this invention, electronic switch circuits 28 and 38 are added to conventional constant current source circuits 20 and 30, and a constant current is turned on and off by these switch operations. When an input signal VIN is in the low level in the constant current source circuit 20', the transistor TR28 operating as the electronic switch is turned off, and a divided voltage of a power source VCC is given to the base of a TR21, and a constant current if is flowed. When the input signal VIN becomes on a high level ''H'', the TR28 is turned on, and the constant current if is not flowed, and a pulse voltage VOUT is generated. In this case, rise time tr and breaking time tf of the output pulse voltage are not affected because a constant current value is set independently of the crest value of the input signal VIN. |
