Mobile communication apparatus including dividers in transmitter and receiver

A transceiver comprising:

• a variable gain low pass filter receiving a baseband signal;
• and
• an offset voltage canceling circuit including means for canceling a DC offset voltage of said variable gain low pass filter,
• said variable gain low pass filter including a variable gain amplifier and a low pass filter;
• wherein said offset voltage canceling circuit includes an analog-to-digital converter (ADC) receiving an output signal of said variable gain amplifier, a controller for detecting a DC offset voltage of said variable gain amplifier from an output signal of said ADC to output a signal for canceling said DC offset voltage, and a digital-to-analog converter (DAC) receiving the output signal of said controller to output a signal to said variable gain amplifier;
• said variable gain amplifier comprises first and second transistors having their emitters connected to each other, a first resistor connected to a collector of said first transistor and a power supply, a second resistor connected to a collector of said second transistor and said power supply, and a variable current source connected to said emitters, wherein a signal is inputted from bases of said first and second transistors, and a signal is outputted from the collectors of said first and second transistors;
• and
• said DAC comprises a plurality of voltage-to-current converters each including a third transistor and a third resistor connected to the emitter of said third transistor and a ground, said third transistor having a collector connected to the collector of said first transistor, and said third transistor having a base connected to an output of said controller.

A transceiver comprising:

• a variable gain low pass filter receiving a baseband signal;
• and
• an offset voltage canceling circuit including means for canceling a DC offset voltage of said variable gain low pass filter,
• said variable gain low pass filter including a variable gain amplifier and a low pass filter;
• wherein said variable gain low pass filter comprises a differential circuit;
• said variable gain amplifier is a chopper type amplifier having first and second input terminals and first and second output terminals;
• said chopper type amplifier includes a third variable gain amplifier having third and fourth input terminals and third and fourth output terminals, a first switch, and a second switch;
• and
• said first and second switches are controlled to switch between a first state in which said first input terminal is connected to said third input terminal;
• said second input terminal to said fourth input terminal;
• said first output terminal to said third output terminal;
• and said second output terminal to said fourth output terminal, and a second state in which said first input terminal is connected to said fourth input terminal;
• said second input terminal to said third input terminal;
• said first output terminal to said fourth output terminal;
• and said second output terminal to said third output terminal, said first and second states being periodically switched.