Low noise amplifier and differential amplifier

A differential amplifier comprising:

• a first transformer having a primary winding whose one end is connected to a first signal input terminal to which a first input signal is applied, and a secondary winding electromagnetically coupled to the primary winding;
• a first input-stage transistor having a control electrode, a first conduction electrode and a second conduction electrode, the first and second conduction electrodes changing a conduction state by the control electrode, and the control electrode being connected to a terminal of the primary winding of the first transformer other than the terminal connected to the first signal input terminal;
• a first upper-stage transistor having a control electrode, a first conduction electrode and a second conduction electrode, the first and second conduction electrodes changing a conduction state by the control electrode, the second conduction electrode being connected to a first load device, and the first conduction electrode being connected to the second conduction electrode of the first input-stage transistor so that the first upper-stage transistor is connected to the first input-stage transistor in a cascode connection manner, thereby enhancing an output impedance;
• a first amplification-result transmission circuit providing an amplification result of the first input signal to a first output node;
• a first negative feedback circuit applying an amplification result of the first input signal on the first output node to the secondary winding of the first transformer;
• a second negative feedback circuit connected between the first output node and the first signal input terminal;
• a second transformer having a primary winding whose one end is connected to a second signal input terminal to which a second input signal is applied, and a secondary winding electromagnetically coupled to the primary winding;
• a second input-stage transistor having a control electrode, a first conduction electrode and a second conduction electrode, the first and second conduction electrodes changing a conduction state by the control electrode, and the control electrode being connected to a terminal of the primary winding of the second transformer other than the terminal connected to the second signal input terminal;
• a second upper-stage transistor having a control electrode, a first conduction electrode and a second conduction electrode, the first and second conduction electrodes changing a conduction state by the control electrode, the second conduction electrode being connected to a second load device, and the first conduction electrode being connected to the second conduction electrode of the second input-stage transistor so that the second upper-stage transistor is connected to the second input-stage transistor in a cascode connection manner, thereby enhancing an output impedance;
• a second amplification-result transmission circuit providing an amplification result of the second input signal to a second output node;
• a third negative feedback circuit applying an amplification result of the second input signal on the second output node to the secondary winding of the second transformer;
• a fourth negative feedback circuit connected between the second output node and the second signal input terminal;
• a constant current circuit connected to a current path, including the first input-stage transistor, the first upper-stage transistor and the first load device, and a current path, including the second input-stage transistor, the second upper-stage transistor, and the second load device;
• a first phase compensation circuit connected to the first output node and the control electrode of the first upper-stage transistor;
• a second phase compensation circuit connected to the first output node and the control electrode of the first input-stage transistor;
• a third phase compensation circuit connected to the second output node and the control electrode of the second upper-stage transistor;
• and
• a fourth phase compensation circuit connected to the second output node and the control electrode of the second input-stage transistor.

A low noise amplifier comprising:

• a signal input terminal to which an input signal is applied;
• a transformer having a primary winding whose one end is grounded, and a secondary winding electromagnetically coupled to the primary winding;
• an input-stage transistor having a control electrode, a first conduction electrode, and a second conduction electrode, the first and second conduction electrodes changing a conduction state by the control electrode, the control electrode being connected to the signal input terminal, and the first conduction electrode being connected to a terminal of the primary winding other than the terminal grounded;
• an upper-stage transistor having a control electrode, a first conduction electrode and a second conduction electrode, the first and second conduction electrodes changing a conduction state by the control electrode, the second conduction electrode being connected to a load device, the first conduction electrode being connected to the second conduction electrode of the input-stage transistor so that the upper-stage transistor is connected to the input-stage transistor in a cascode connection manner, thereby enhancing an output impedance;
• an amplification-result transmission circuit providing an amplification result of the input signal to an output node;
• a first negative feedback circuit applying an amplification result of the input signal on the output node to the secondary winding;
• a second negative feedback circuit connected between the output node and the control electrode of the input-stage transistor;
• a first phase compensation circuit connected to the output node and the control electrode of the upper-stage transistor;
• and
• a second phase compensation circuit connected to the output node and the control electrode of the input-stage transistor.