Sharp Kabushiki Kaisha Corporation

Toshihiko Shigenari

Toshihide Miyake

Transistors Q11 and Q12 constitute a first differential amplifier, their emitters are connected with each other by a resistor R1 and also connected respectively to constant-current sources CS11 and CS12. Transistors Q15 to Q17 constitute a second differential amplifier, and the collector of the transistor Q16 is connected with a current mirror 17. This current mirror circuit 17 is constituted by transistors Q18 and Q19 and resistors R3 and R4. The capacitor 22 is supplied with a current from the current mirror circuit 17, and its voltage is fed back through a buffer circuit 14 to the base of the transistor Q12 as a component of the first differential amplifier.

Filter circuit for integrated circuit

A balanced modulation circuit includes first, second, and third differential amplifiers. The first differential amplifier includes first and second transistors (Q11, Q12) having the emitters connected to first and second constant-current sources (CS11, CS12) and also connected with each other through a resistor, the collectors connected to the power supply line through respective base-collector-coupled transistors (Q13, Q14) used as diodes, and the bases connected to a first voltage source (V11) through respective resistors (R11, R12). The second differential amplifier includes third and fourth transistors (Q17, Q18) having the emitters connected to the collector of a transistor (Q15) whose base is connected to the base of the transistor (Q14) and whose emitter is connected to the power supply line, the bases of the third and fourth transistors (Q17, Q18) are connected to a second voltage source (V12) through respective resistors, and the collectors are connected to the ground line through respective resistors. The third differential amplifier includes fifth and sixth transistors (Q19, Q20) having the emitters connected to the collector of a transistor (Q16) whose base is connected to the base of the transistor (Q13) and whose emitter is connected to the power supply line, the bases of the fifth and sixth transistors (Q19, Q20) are respectively connected to the bases of the fourth and third transistors (Q18, Q17), and the collectors are respectively connected to the collectors of the third and fourth transistors (Q17, Q18).

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Nara, Japan

Toshihiko Shigenari