Low noise analog sampling circuit and a method for low noise sampling of an analog signal

A low noise analog sampling circuit comprising a transistor coupled to a first feedback loop and to a second feedback loop;

• wherein during a first operational phase, the first feedback loop is closed such as to affect a state of the transistor in response to an analog input signal;
• wherein at an end of the first operational phase the first feedback loop is opened and introduces a first noise;
• wherein during a second operational phase the second feedback loop provides the transistor a feedback signal that is responsive to an amplified error signal;
• wherein the error signal represents a difference between (i) a sampled signal representative of a state of the transistor short period before the first feedback loop is opened and (ii) a signal representative of a current state of the transistor;
• wherein at an end of the second operational phase the second feedback loop is opened and introduces a second noise that is attenuated by multiple capacitors of the second feedback loop such as to provide an attenuated second noise that substantially smaller than the first noise;
• wherein during another operational phase the transistor outputs an output signal responsive to the analog input signal and to the attenuated second noise;
• and wherein the second feedback loop comprises a second capacitor that is charged, during the second operational phase, to a voltage level that is responsive to the amplified error signal;
• wherein the amplified error signal is provided to the second capacitor via a third switch;
• wherein at the end of the second operational phase the third switch is opened and introduces the second noise to the second capacitor;
• and
• wherein the second noise is attenuated by a third and a fourth capacitors of the second feedback loop such as to provide to the transistor an attenuated second noise.

A low noise analog sampling circuit comprising a transistor coupled to a first feedback loop and to a second feedback loop;

• wherein during a first operational phase, the first feedback loop is closed such as to affect a state of the transistor in response to an analog input signal;
• wherein at an end of the first operational phase the first feedback loop is opened and introduces a first noise;
• wherein during a second operational phase the second feedback loop provides the transistor a feedback signal that is responsive to an amplified error signal;
• wherein the error signal represents a difference between (i) a sampled signal representative of a state of the transistor short period before the first feedback loop is opened and (ii) a signal representative of a current state of the transistor;
• wherein at an end of the second operational phase the second feedback loop is opened and introduces a second noise that is attenuated by multiple capacitors of the second feedback loop such as to provide an attenuated second noise that substantially smaller than the first noise;
• wherein during another operational phase the transistor outputs an output signal responsive to the analog input signal and to the attenuated second noise;
• and
• wherein second noise is attenuated by an attenuation factor that is responsive to a relationship between a capacitance of third and fourth capacitors.

A low noise analog sampling circuit comprising a transistor coupled to a first feedback loop and to a second feedback loop;

• wherein during a first operational phase, the first feedback loop is closed such as to affect a state of the transistor in response to an analog input signal;
• wherein at an end of the first operational phase the first feedback loop is opened and introduces a first noise;
• wherein during a second operational phase the second feedback loop provides the transistor a feedback signal that is responsive to an amplified error signal;
• wherein the error signal represents a difference between (i) a sampled signal representative of a state of the transistor short period before the first feedback loop is opened and (ii) a signal representative of a current state of the transistor;
• wherein at an end of the second operational phase the second feedback loop is opened and introduces a second noise that is attenuated by multiple capacitors of the second feedback loop such as to provide an attenuated second noise that substantially smaller than the first noise;
• wherein during another operational phase the transistor outputs an output signal responsive to the analog input signal and to the attenuated second noise;
• and
• wherein the second feedback loop comprises an amplifier that comprises a first input and a second input,
• the first input of the amplifier is coupled to a drain of the transistor and the second input of the amplifier is coupled to a second end of a second switch;
• wherein a first end of the second switch is coupled to the drain of the transistor;
• wherein short period before the first feedback loop is opened the second switch is opened so that the first capacitor stores a sampled signal representative of the state of the transistor short period before the first feedback loop is opened;
• and
• wherein the amplifier outputs, during the second operational phase, the amplifier error signal.

A method for low noise sampling of an analog signal, the method comprises:

• receiving an analog input signal;
• closing, during a first operational phase, a first feedback loop that is coupled to a transistor, such as to affect a state of the transistor in response to the analog input signal;
• opening, at an end of the first operational phase, the first feedback loop such as to introduce a first noise;
• providing, during a second operational phase, to the transistor and by a second feedback loop, a feedback signal that is responsive to an amplified error signal;
• wherein the error signal represents a difference between (i) a sampled signal representative of a state of the transistor short period before the first feedback loop is opened and (ii) a current state of the transistor;
• opening, at an end of the second operational phase, the second feedback loop such as to introduce a second noise;
• attenuating the second noise signal by multiple capacitors of the second feedback loop, such as to provide an attenuated second noise that substantially smaller than the first noise;
• outputting, during another operational phase, an output signal responsive to the analog input signal and to the attenuated second noise;
• and
• closing, during the first operational phase the second feedback loop, and setting an amplifier of the second feedback loop to a non-amplifying state.

A method for low noise sampling of an analog signal, the method comprises:

• receiving an analog input signal;
• closing, during a first operational phase, a first feedback loop that is coupled to a transistor, such as to affect a state of the transistor in response to the analog input signal;
• opening, at an end of the first operational phase, the first feedback loop such as to introduce a first noise;
• providing, during a second operational phase, to the transistor and by a second feedback loop, a feedback signal that is responsive to an amplified error signal;
• wherein the error signal represents a difference between (i) a sampled signal representative of a state of the transistor short period before the first feedback loop is opened and (ii) a current state of the transistor;
• opening, at an end of the second operational phase, the second feedback loop such as to introduce a second noise;
• attenuating the second noise signal by multiple capacitors of the second feedback loop, such as to provide an attenuated second noise that substantially smaller than the first noise;
• outputting, during another operational phase, an output signal responsive to the analog input signal and to the attenuated second noise;
• and
• charging, during the second operational phase, a second capacitor of the second feedback loop to a voltage level that is responsive to the amplified error signal;
• wherein the providing comprises providing the amplified error signal to the second capacitor via a third switch;
• wherein the opening comprises opening the third switch such as to introduce the second noise to the second capacitor;
• and wherein the attenuating comprises attenuating the second noise by a third and a fourth capacitors of the second feedback loop.

A method for low noise sampling of an analog signal, the method comprises:

• receiving an analog input signal;
• closing, during a first operational phase, a first feedback loop that is coupled to a transistor, such as to affect a state of the transistor in response to the analog input signal;
• opening, at an end of the first operational phase, the first feedback loop such as to introduce a first noise;
• providing, during a second operational phase, to the transistor and by a second feedback loop, a feedback signal that is responsive to an amplified error signal;
• wherein the error signal represents a difference between (i) a sampled signal representative of a state of the transistor short period before the first feedback loop is opened and (ii) a current state of the transistor;
• opening, at an end of the second operational phase, the second feedback loop such as to introduce a second noise;
• attenuating the second noise signal by multiple capacitors of the second feedback loop, such as to provide an attenuated second noise that substantially smaller than the first noise;
• and
• outputting, during another operational phase, an output signal responsive to the analog input signal and to the attenuated second noise;
• wherein the attenuating comprises attenuating by an attenuation factor that is responsive to a relationship between a capacitance of third and fourth capacitors that belong to the second feedback loop.