Figure 6.

THD (a) and third order IMD (the reference impedance equals 50 Ω) (b) measured with the gain of the Chebyshev notch channel set at 60 dB. (a) After examining the available dynamic range of the channel (from 1 μV peak to 2.3 mV peak), it is clear that the achieved THD is less than 0.2%. (b) The two tones applied to the Chebyshev notch channel were f₁ = 4.9 Hz and f₂ = 5.1 Hz. The output power of a single fundamental tone (in dBm—red line in the graph) and the relative amplitude of the third order IMD₃ products referenced to a single tone (blue circles in figure (b)) are plotted as a function of the applied input power. The third order intercept line (dashed blue line) is extended to intersect the extension of the fundamental output signal line (dashed red line). This intersection is termed the third order intercept point IP₃. The calculated IP₃ is characterized by a relatively high value, which is a positive result since the higher the IP₃ values the better the linearity of the amplifier and the weaker the output intermodulation products that will be generated at the amplifier’s output.