A MOS cascode push-pull RF power amplifier with reduced temperature variation of gain

摘要

The variation of gain with temperature in a MOS cascode radio frequency power amplifier is reduced by biasing the common-source input transistors M11 and M12 with a current 20 that has a positive temperature coefficient while biasing the cascode transistors M21 and M22 with a voltage proportional to a current 24 having a negative temperature coefficient. It has been found that a gain variation of less than 1dB across the range from -40 C to 120 C may be achieved, without any worsening of the distortion and compression performance, when the magnitude of the positive temperature coefficient exceeds the magnitude of the negative temperature coefficient. The current source 20 may be generaed (28, figure 2) by subtracting a CTAT (complementary to absolute temperature) current from a PTAT (proportional to absolute temperature) current. The current sources 20 and 24 may be programmed by use of switches (figure 3 and 4).