Industrial Technology Research Institute

Wei-Tsung Li

Jeng-Han Tsai

Shih-Ming Wang

Chih-Chun Shen

Yi-Tso Cheng

Chia-Lung Lin

Gao-Ching Lin

A variable gain amplifier (VGA) is provided. The VGA includes at least one amplifier circuit, at least one current-steering circuit and at least one bias voltage circuit. Each current-steering circuit is coupled to its corresponding amplifier circuit. Each bias voltage circuit is coupled to its corresponding current-steering circuit to provide a positive bias voltage to each current-steering circuit.

Variable gain amplifier and method thereof

A bias circuit includes a buffer, a temperature compensation circuit, and a feedback circuit. The buffer includes a first transistor. A first terminal of the first transistor and a second terminal of the first transistor are electrically connected with a first voltage source. A third terminal of the first transistor is electrically connected with an external amplifier. The temperature compensation circuit includes a second transistor and a temperature compensation component. A first terminal of the second transistor is electrically connected with the third terminal of the first transistor. Two terminals of the temperature compensation component are electrically connected with a second terminal of the second transistor and the first voltage source respectively. A third terminal of the second transistor is grounded. The feedback circuit is electrically connected with the first terminal of the first transistor and the second terminal of the second transistor.

Bias circuit

An embodiment provides a variable gain amplifying method includes: on a signal path of a radio frequency input signal, amplifying a radio frequency input signal by a plurality of serially-coupled amplifiers; steering currents from the amplifiers and controlling respective gains of the amplifiers; performing gain match on the signal path of the radio frequency input signal; and performing phase compensation on the signal path of the radio frequency input signal. The signal path of the radio frequency input signal further has first and second phase variation trends which compensate each other.

A power amplifier circuit including a power transistor, a variable impedance circuit, first and second envelope detecting circuits is provided. The power transistor receives an input signal and outputs an output signal. The variable impedance circuit includes an impedance control transistor and a first filter capacitor. An equivalent impedance of the variable impedance circuit varies with the input signal. The impedance control transistor is coupled to the power transistor and receives a control voltage. The first filter capacitor is coupled between the impedance control transistor and ground. Both the first and the second envelope detecting circuits detect the input signal to dynamically control the equivalent impedance of the variable impedance circuit.

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Taipei, Taiwan

Wei-Tsung Li