Amplifying circuit for an integrated circuit with low-noise characteristic

A semiconductor device having a semiconductor integrated circuit, comprising;

• a first transistor having a base of an input terminal, to which a first base bias is supplied,
• a second transistor having a collector connected to a voltage source, a base supplied with a second base bias and an emitter of an output terminal,
• a parallel circuit of a constant current source connected to an emitter of the first transistor and a first condenser,
• an inductor connected between a collector of the first transistor and an emitter of the second transistor;
• and
• a second condenser connected between the collector of the first transistor and the base of the second transistor,
• wherein the size of the emitter of the first transistor is larger than that of the second transistor.

A transistor differential amplifier circuit comprising:

• a differential pair including first and second transistors, first and second resistors connected to collectors of the first and second transistors and a constant current source connected commonly to emitters of the first and second transistors;
• a third transistor, an emitter of which is connected to a connection point of the first and second resistors and outputs an output signal;
• a first condenser connected between the collector of the first transistor and a base of the third transistor;
• and
• a voltage source connected directly to a collector of the third transistor.

A transistor differential amplifier circuit comprising;

• a differential pair including first and second transistors, first and second inductors connected to collectors of the first and second transistors and a constant current source connected commonly to emitters of the first and second transistors, a third transistor, an emitter of which is connected to a connection point of the first and second inductors,
• a first condenser connected between the collector of the first transistor and a base of the third transistor;
• and
• a voltage source connected to the collector of the third transistor,
• an output being outputted from the emitter of the third transistor.

A transistor amplifying circuit comprising:

• a differential pair including first and second transistors, a base of the first transistor being supplied with an input signal and a base of the second transistor being supplied with a control signal, first and second resistors connected to collectors of the first and second transistors, and a constant current source connected commonly to emitters of the first and second transistors;
• a third transistor, an emitter of which is connected to a connection point of the first and second resistors and outputs an output signal;
• a first condenser connected between the collector of the first transistor and a base of the third transistor;
• a second condenser connected between the base of the second transistor and the ground;
• a voltage source connected directly to the collector of the third transistor;
• third and fourth resistors;
• a constant voltage source for providing base biases to the bases of the first and second transistors via the third and fourth resistors, respectively;
• and
• a fifth resistor connected between the base of the third transistor and the voltage source for providing a base bias to the base of the third transistor from the voltage source.

A transistor amplifying circuit comprising:

• a differential pair including first and second transistors, first and second resistors connected to collectors of the first and second transistors, and a constant current source connected commonly to emitters of the first and second transistors;
• a third transistor, an emitter of which is connected to a connection point of the first and second resistors and outputs an output signal;
• a first condenser connected between the collector of the first transistor and a base of the third transistor;
• and
• a voltage source connected directly to the collector of the third transistor,
• wherein the sizes of the first and second transistors are same and the size of the third transistor is smaller than that of the first and second transistors.