Reduced area, first order R-C filters using current conveyors

A filter comprising:

• an input terminal and an output terminal;
• a first capacitor coupled to the input terminal;
• a resistor coupled to the input terminal;
• means for providing a first current having a magnitude equal to a constant K1 times the magnitude of a current through the first capacitor;
• means for providing a second current having a magnitude equal to a constant K2 times the magnitude of a current through the resistor;
• and
• a second capacitor coupled between the output terminal and a reference voltage, wherein the second capacitor and the first and second currents control an output voltage at the output terminal.

A phase-locked loop comprising:

• a loop filter which includes:
• an input terminal and an output terminal;
• a first capacitor coupled to the input terminal;
• a first current conveyor coupled between the first capacitor and the output terminal;
• a resistor coupled to the input terminal;
• a second current conveyor coupled between the resistor and the output terminal;
• and a second capacitor coupled between the output terminal and a reference voltage;
• a voltage controlled oscillator coupled to the output terminal of the loop filter;
• a phase comparator coupled to the voltage controlled oscillator;
• and
• a charge pump coupled to the phase comparator and to the input terminal of the loop filter, wherein the charge pump pumps up a voltage on the input terminal of the loop filter in response to a signal from the phase comparator indicating that a voltage to the voltage controlled oscillator should be decreased.