Amplifier device

An amplifier device comprising:

• an amplifying unit having a first end coupled to a voltage source configured to receive a source voltage, a second end configured to receive an input signal, and a third end coupled to a first reference potential terminal configured to receive a first reference potential, wherein the first end of the amplifying unit is configured to output an output signal amplified by the amplifying unit;
• and
• a bias module coupled to the second end of the amplifying unit, configured to receive a voltage signal to provide a bias current to the amplifying unit, and comprising a variable current source comprising:
• an operational amplifier comprising a first input end coupled to a first signal terminal and configured to receive a first reference signal, a second input end coupled to a second signal terminal and configured to receive the voltage signal, and an output end configured to output an output voltage;
• a first resistor comprising a first end coupled to the second input end of the operational amplifier, and a second end coupled to the output end of the operational amplifier;
• a voltage-to-current convertor comprising a first end coupled to the output end of the operational amplifier, and a second end coupled to the second end of the amplifying unit, and configured to convert the output voltage into the bias current;
• a second resistor comprising a first end coupled to the first signal terminal, and a second end coupled to the first input end of the operational amplifier;
• and
• a third resistor comprising a first end coupled to the second signal terminal, and a second end coupled to the second input end of the operational amplifier;
• wherein the voltage signal is a variable voltage;
• and
• wherein a supply current flowing into the amplifying unit is adjusted in accordance with the voltage signal to stay within a predetermined range.