Low phase error amplifying

Amplifying apparatus having a nearly zero phase error in a desired frequency band, said apparatus comprising:

• an amplifier, having inverting and noninverting inputs and an output, constructed and arranged to operate as a low pass filter with a high gain and to have a cut-off frequency substantially below said frequency band,
• a signal input node adapted to introduce an input voltage to said inverting input,
• a signal output node adapted to obtain an output voltage from said output of said amplifier,
• a capacitor-resistor network constructed and arranged to provide, in connection with said amplifier, substantially 180 degree phase shift between said input voltage and said output voltage in said frequency band, and
• a resistive global feedback loop connecting said signal input and signal output nodes adapted to control the closed loop gain of the amplifying apparatus.

Amplifying apparatus having a nearly zero phase error in a frequency band, said apparatus comprising:

• at least two cascaded amplifiers including local feedback loops formed by a network constructed and arranged to exhibit a high forward gain,
• said local feedback loops constructed and arranged to establish a predetermined restricted pass band containing said frequency band,
• said network creating, in said frequency band, substantially 180.degree. phase shift between an input voltage and an output voltage of said amplifying apparatus,
• a resistive global feedback loop arranged to connect the output of the second amplifier and the input of the first amplifier, and
• said global feedback loop adapted to control the closed loop gain of said amplifying apparatus.

Amplifying apparatus having a nearly zero phase error in a desired frequency band, said apparatus comprising:

• at least one amplifier, having inverting and noninverting inputs and an output, including a local feedback loop formed by a network, all constructed and arranged to exhibit a high forward gain in said frequency band,
• a signal input node adapted to introduce an input voltage to said inverting input,
• a signal output node adapted to obtain an output voltage from said output of said amplifier,
• said amplifier and said network constructed and arranged to exhibit substantially 180 degree phase shift between said input voltage and said output voltage in said frequency band, and
• a resistive global feedback loop connecting said signal input and signal output nodes adapted to control the closed loop gain of the amplifying apparatus.