Integration circuit including a differential amplifier having a variable transconductance

An integration circuit comprising:

• a differential amplifier including current sources connected to a voltage source, and at least first and second bipolar transistors having emitter electrodes and base electrodes connected to input terminals, and collector electrodes connected to the current sources, respectively, the first and second bipolar transistors serving as amplifying elements;
• a capacitor connected between the collectors of the first and second bipolar transistors, for serving as a load of the differential amplifier;
• and
• first and second field effect transistors connected in parallel to each other, the first and second field effect transistors having gate electrodes respectively connected to the base electrodes of the first and second bipolar transistors.

An integration circuit comprising:

• a differential amplifier including at least first and second current sources, and at least first and second bipolar transistors having emitter electrodes, collector electrodes respectively connected to the first and second current sources and base electrodes connected to input terminals, said first and second transistors serving as amplifying elements;
• a capacitor connected between said collectors of said first and second bipolar transistors, serving as a load of said differential amplifier;
• a variable resistance circuit connected between the emitter electrodes of said first and second bipolar transistors, the resistance of which is variable;
• and
• voltage controlled current source means connected between the collector and emitter electrodes of each of the first and second bipolar transistors, for feeding back signals corresponding to collector currents of said first and second bipolar transistors to the emitter electrodes.

An integration circuit comprising:

• a differential amplifier comprising first and second FETs, which have gate electrodes respectively connected to input terminals, drain electrodes respectively connected to output terminals, and source electrodes;
• a capacitor connected between the source electrodes of the first and second FETs;
• current sources respectively connected between the source electrodes of the first and second FETs and a power source, for determining the current value of the differential amplifier;
• and
• a variable resistance circuit connected between the drain electrodes of the first and second FETs.