Amplifier with gain adjustment resistor, feedback resistors and transistors and optical receiver including amplifier

An optical receiver comprising:

• an optical detector configured to convert received signal light into current;
• and
• an amplifier circuit, including:
• a first transistor of which a collector or a drain is coupled to a first power source via a first load resistor;
• a second transistor of which a collector or a drain is coupled to the first power source via a second load resistor;
• a gain adjustment resistor that is connected to an emitter or a source of the first transistor and an emitter or a source of the second transistor;
• a first current source that is connected to the emitter or the source of the first transistor and a second power source;
• a second current source that is connected to the emitter or the source of the second transistor and the second power source;
• a third transistor of which a collector or a drain is connected to the first power source and a base or a gate is connected to the first load resistor;
• a fourth transistor of which a collector or a drain is connected to the first power source and a base or a gate is connected to the second load resistor;
• a first feedback resistor that is directly connected to a base or a gate of the first transistor and directly connected to an emitter or a source of the third transistor;
• a second feedback resistor that is directly connected to a base or a gate of the second transistor and directly connected to an emitter or a source of the fourth transistor;
• a fifth transistor that is directly connected to the collector or the drain of the first transistor in series;
• and
• a sixth transistor that is directly connected to the collector or the drain of the second transistor in series,
• wherein the amplifier circuit converts current, the current being generated in the optical detector, into voltage and amplifies the current, and
• wherein a collector or a drain of the fifth transistor is connected to the base or the gate of the third transistor and a collector or a drain of the sixth transistor is connected to the base or the gate of the fourth transistor.