Delay circuit having a constant delay time

A delay circuit having a constant delay time, comprising:

• an electric wire for transmitting a signal;
• a capacitor connected to said electric wire in parallel and for delaying the transmission of said signal;
• a current controlling transistor connected to said capacitor in parallel, and coupled between said electric wire and the ground;
• and
• a reference voltage generator at its output terminal connected to a gate of said current controlling transistor, and for varying an amount of an electric current flowing through said current controlling transistor when a level of a voltage applied to said capacitor is changed, thereby keeping an amount of an electric current flowing through said capacitor constant.

A delay circuit having a constant delay time, comprising:

• an inverter for inverting an input signal to generate an output signal;
• an electric wire for transmitting said output signal;
• a capacitor connected between said electric wire and a terminal of the source voltage, and for delaying the transmission of said output signal;
• a first current controlling transistor connected to said capacitor in parallel, and connected between said electric wire and a terminal of the voltage source;
• first switching means connected to a gate of said first current controlling transistor, and operated in response to a first control signal which is enabled when a level of a voltage applied to said capacitor varies, whereas it is disabled to turn off said first current controlling transistor when that of the voltage goes constant;
• and
• a first reference voltage generator at its output terminal connected to said first switching means, and for varying an amount of an electric current flowing through said first current controlling transistor when a level of a voltage applied to said capacitor is changed, thereby keeping an amount of an electric current flowing through said capacitor constant.

A delay circuit having a constant delay time, comprising:

• an inverter for inverting an input signal to generate an output signal;
• an electric wire for transmitting said output signal;
• a capacitor connected between said electric wire and the ground, and for delaying the transmission of said output signal;
• a first current controlling transistor connected to said capacitor in parallel, and connected between said electric wire and the ground;
• first switching means connected to a gate of said first current controlling transistor, and for increasing an amount of the electric current flowing through said first current controlling transistor when a voltage applied to said capacitor is increased, thereby causing the amount of the electric current flowing through said capacitor to be kept constant;
• a second current controlling transistor connected between said electric wire and a terminal of the source voltage;
• and
• second switching means connected to a gate of said second current controlling transistor, and for decreasing an amount of the electric current flowing through said second current controlling transistor when a voltage applied to said capacitor is decreased, thereby causing the amount of the electric current flowing through said capacitor to be kept constant.