Wave forming circuit of an electronic tone generator
AssigneeIndustrial Technology Research Institute
InventorShyuh-Der Lin
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Abstract
Circuitry for an electronic tone generator effectively isolates a tone modulating RC network from the electroacoustic output device and associated volume control systems. This isolation prevents low or variable impedance of the output portion of the generator from adversely affecting the charge and discharge rate of the RC network. Isolation circuitry includes a MOSFET connected in a source follower circuit to convert the voltage signal from the RC network to a comparable current signal which is amplified through a pair of MOSFETs in a current mirror circuit.
Claims4
An electronic tone generator employing an RC network comprising a capacitor capable of being charged and discharged and a resistor through which said capacitor is discharged and in which the charging and discharging of the capacitor is utilized to amplitude modulate a tone signal, and the modulated tone signal is converted to audible sound by an electroacoustic output device, the improvement comprising a first MOS transistor in said RC network for limiting the discharge of said capacitor through said resistor, said transistor exhibiting a threshold voltage which enables said transistor to shut off to prevent complete discharge of said capacitor beyond the threshold voltage of said transistor, and means isolating said RC network from the impedance of said output device, said isolating means comprising a source follower second MOS transistor circuit between said RC network and said output device.
Dependencies are inferred from the claim text.