Complementary variable gain amplification

An apparatus comprising:

• a variable gain amplifier including multiple amplifiers, the multiple amplifiers including at least one first amplifier and at least one second amplifier cascaded together in series;
• the first amplifier including:
• a first input node configured to accept a first reference current;
• a first output node;
• a first set of transistors having a first doping type;
• and
• first mirroring means for producing at least a portion of a second reference current at the first output node based on the first reference current via at least a portion of the first set of transistors, the first mirroring means forming at least a portion of one or more amplifier branches of the first amplifier, the amplifier branches coupled together via the first output node;
• and
• the second amplifier including:
• a second input node coupled to the first output node;
• and
• a second set of transistors having a second doping type, at least a portion of the second set of transistors configured to be biased via the second reference current.

A method for complementary variable gain amplification, the method comprising:

• accepting, via a first amplifier comprising a first set of transistors having a first doping type, an input signal that comprises a first intermediate-frequency signal and a first reference current;
• producing, via the first set of transistors, a first amplified signal comprising a second intermediate-frequency signal and a second reference current, the second reference current based on the first reference current, the second intermediate frequency signal based on the first intermediate-frequency signal, at least a portion of the first set of transistors forming one or more amplifier branches of the first amplifier, the one or more amplifier branches coupled together via a first output node of the first amplifier;
• biasing, using the second reference current, a second amplifier comprising a second set of transistors having a second doping type, the second amplifier coupled to the first amplifier via the first output node such that the first amplifier and the second amplifier are cascaded together in series;
• and
• producing, via the second set of transistors, a second amplified signal comprising a third intermediate-frequency signal, the third intermediate-frequency signal based on the second intermediate-frequency signal.

A variable gain amplifier comprising:

• a first amplifier including:
• a first input node;
• a first output node;
• at least a first amplifier branch;
• a first passive load coupled to the first amplifier branch;
• a first capacitor coupled between the first output node and the first passive load;
• a first current-reuse branch coupled to the first output node;
• and
• a first set of transistors having a first doping type, the first set of transistors configured to implement a first current mirror, different portions of the first current mirror are included as parts of the first amplifier branch and the first current-reuse branch;
• and
• an active load coupled to the first output node, the active load comprising at least one transistor having a second doping type.