Open-collector variable gain amplifier and method therefor

A semiconductor device comprising an amplifier circuit, including:

• a variable gain amplifier including an input receiving an input signal and an open-conduction output having no other connection within the variable gain amplifier, wherein the variable gain amplifier includes,
• (a) a first transistor including a control terminal coupled for receiving a first component of the input signal,
• (b) a second transistor including a control terminal coupled for receiving a second component of the input signal,
• (c) a third transistor including a control terminal coupled for receiving a first component of a control signal and a first conduction terminal coupled to a first conduction terminal of the first transistor and a second conduction terminal being a first terminal of the open-conduction output of the variable gain amplifier having no other connection within the variable gain amplifier, and
• (d) a fourth transistor including a control terminal coupled for receiving a second component of the control signal and a first conduction terminal coupled to a first conduction terminal of the second transistor and a second conduction terminal being a second terminal of the open-conduction output of the variable gain amplifier having no other connection within the variable gain amplifier;
• and
• an output stage including an input coupled to the open-conduction output of the variable gain amplifier and an output providing an output signal of the amplifier circuit.

A method of making a semiconductor device comprising an amplifier circuit, including:

• providing a substrate;
• forming a variable gain amplifier including an input receiving an input signal and an open-conduction output over the substrate, wherein forming the variable gain amplifier includes,
• (a) providing a first transistor including a control terminal coupled for receiving a first component of the input signal,
• (b) providing a second transistor including a control terminal coupled for receiving a second component of the input signal,
• (c) providing a third transistor including a control terminal coupled for receiving a first component of a control signal and a first conduction terminal coupled to a first conduction terminal of the first transistor and a second conduction terminal being a first terminal of the open-conduction output of the variable gain amplifier having no other connection within the variable gain amplifier, and
• (d) providing a fourth transistor including a control terminal coupled for receiving a second component of the control signal and a first conduction terminal coupled to a first conduction terminal of the second transistor and a second conduction terminal being a second terminal of the open-conduction output of the variable gain amplifier having no other connection within the variable gain amplifier;
• and
• forming an output stage including an input coupled to the open-conduction output of the variable gain amplifier and an output providing an output signal of the amplifier circuit over the substrate.