Transistor Mixers

A general expression yielding theoretical limiting values for average conversion transconductance, ¿c;, as a function of oscillator driving voltage and DC bias current is developed. This expression, together with a modification that accounts for effective resistance in series with the junction, is applicable to all present-day junction transistors. Theoretical and experimental results are compared. Good agreement with theory is postulated for low-cost, mass-produced, transistors up to at least 50 MHz.