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Mixer Design
Mixer Design 331
Figure 7.16 An active distributed mixer based on the JFET.
Figure 7.17 A popular IC active mixer.
7.2.4 Active mixer issues
When Gilbert cell IC active mixers (Fig. 7.13) are operated at low frequencies,
a square-wave local oscillator must be used to decrease the steadily rising NF
of the mixer caused by the longer off times of the mixer quad transistors (Q ,
3
Q , Q , Q ). A square wave will minimize these off times.
4 5 6
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