Low noise communication analog compressor and analog expander

An analog expander circuit comprising:

• a rectifier circuit for rectifying an input signal;
• a first analog signal processing circuit having first to fourth input terminals and first and second output terminals, and designed to operate such that said first and second output terminals are set at the same potential and that a current difference between said first and second output terminals is proportional to a product of a potential difference between said first and second input terminal and a potential difference between said third and fourth input terminal, said first, second, third and fourth input terminals connected to receive the input signal, a first reference potential, a second reference potential, and a difference between the second reference potential and an output potential of said rectifier circuit, respectively;
• an operational amplifier circuit having a positive input terminal and a negative input terminal connected to the second and first output terminals of said first analog signal processing circuit, respectively;
• second analog signal processing circuit having first to fourth input terminals and first and second output terminals connected to the negative and positive input terminals of said operational amplifier circuit, respectively, and designed to operate such that said first and second output terminals are set at the same potential and that a current difference between said first and second output terminals is proportional to a product of a potential difference between said first and second input terminal and a potential difference between said third and fourth input terminal, said first, second, third and fourth input terminals connected to receive an output signal of said operational amplifier circuit, a third reference potential, the second reference potential, and a fourth reference potential, respectively.

An analog compressor circuit of complementary input type, comprising:

• a first analog compressor section for receiving an input signal which is one of a positive signal and a negative signal which are complementary to each other, and for generating an output signal having a gain of less than 1 with respect to the input signal;
• a second analog compressor section for receiving an input signal which is the other of the positive and negative signals which are complementary to each other, and for generating an output signal having a gain substantially equal to the gain of the output signal of said first analog compressor section;
• and
• an adder circuit for adding the output signal of said second analog compressor section and a signal obtained by inverting the output signal of said first analog compressor section.

An analog expander circuit of complementary input type, comprising:

• a first analog expander section for receiving an input signal which is one of a positive signal and a negative signal which are complementary to each other, and for generating an output signal having a gain of at least 1 with respect to the input signal;
• a second analog expander section for receiving an input signal which is the other of the positive and negative signals which are complementary to each other, and for generating an output signal having a gain substantially equal to the gain of the output signal of said first analog expander section;
• and
• an adder circuit for adding the output signal of said second analog expander section and a signal obtained by inverting the output signal of said first analog expander section.