Transconductance-capacitance filter system

A transconductance-capacitance filter system comprising:

• a transconductance-capacitance filter circuit including a transconductance amplifier and a capacitor;
• an adjusting circuit including an oscillator containing a transconductance amplifier having the same structure as that of the transconductance amplifier of said transconductance-capacitance filter circuit, said adjusting circuit producing a digital adjusting the transconductance of the transconductance amplifier of said oscillator based upon an oscillation signal outputted from said oscillator;
• a register for holding said digital adjusting value supplied from said adjusting circuit;
• a D/A converter for converting said digital adjusting value held in said register into an analog adjusting value which is used to adjust the transconductance of the transconductance amplifier of said transconductance-capacitance filter circuit;
• and
• a temperature compensating circuit for producing such a drive bias current capable of compensating for a variation component of the transconductance values of the transconductance amplifier of said transconductance-capacitance filter circuit with respect to a change contained in ambient temperatures of said transconductance-capacitance filter system based upon externally-supplied temperature data, and capable of driving said D/A converter by said drive bias current,
• wherein said adjusting circuit is operated only when said transconductance-capacitance filter system is initiated.

A transconductance-capacitance filter system comprising:

• a transconductance-capacitance filter circuit including a transconductance amplifier and a capacitor;
• an adjusting circuit including an oscillator containing a transconductance amplifier having the same structure as that of the transconductance amplifier of said transconductance-capacitance filter circuit, said adjusting circuit producing a digital adjusting the transconductance of the transconductance amplifier of said oscillator based upon an oscillation signal outputted from said oscillator;
• a register for holding said digital adjusting value supplied from said adjusting circuit;
• a temperature compensating circuit for producing such a drive bias current capable of compensating for a variation component of the transconductance values of the transconductance amplifier of said transconductance-capacitance filter circuit with respect to a change contained in ambient temperatures of said transconductance-capacitance filter system based upon externally-supplied temperature data, and capable of driving said D/A converter by said drive bias current;
• an adder for executing a digital calculation with respect to said compensating digital adjusting value supplied from said temperature compensating circuit and the digital adjusting value held in said register;
• and
• a D/A converter for converting a digital calculation result supplied form said adder into an analog adjusting value which is used to adjust the transconductance of the transconductance amplifier of said transconductance-capacitance filter circuit,
• wherein said adjusting circuit is operated only when said transconductance-capacitance filter system is initiated.