Radio frequency amplifier circuit

A frequency converter comprising:

• an amplifier circuit having:
• a differential amplifier having a first transistor and a second transistor whose emitters are connected with each other and whose collectors are respectively connected to first and second output terminals for outputting differential signal outputs, a first constant-current source connected between a ground and the common emitters of said first and second transistors, and a first load resistor and a second load resistor respectively connected to collectors of said first and second transistors,
• an amplifier having a third transistor whose emitter is grounded, whose base is connected to an input terminal to which a high frequency signal is applied, and whose collector is connected to a third output terminal for outputting a single signal output and also connected to a base of said first transistor, and a third load resistor connected to the collector of said third transistor, and
• a reference voltage generating circuit having a second constant-current source and a fourth load resistor, whose output is connected to a base of said second transistor;
• a voltage controlled oscillator for outputting said high frequency signal applied to the base of said third transistor;
• a frequency divider for receiving differential signal outputs from said first and second output terminals of said amplifier circuit;
• and
• a phase detector for comparing an output from said frequency divider with a reference signal and for outputting a control signal applied through a feedback loop to a voltage control terminal of said voltage controlled oscillator.