On the feasibility of fT-integration employing reverse-active vertical npn´s

The f_T-integration technique is further investigated through the use of vertical n-p-n transistors operating in a so-called reverse-active mode for frequency tuning range extension. The usual DC-gain enhancement scheme can be deployed to compensate the associated low reverse current gain of such reverse-active devices with no degradation in linearity. An integrator using only reverse-active n-p-n´s was experimentally tested using general purpose n-p-n transistor arrays where it exhibits the DC-gain adjustable over 40 dB with the frequency range more than two octaves (0.86-4.20 MHz). Measured THD and IMD3 are below -48 dB and -46 dB respectively for output current signal peak at 50% modulation index, with SFDR=48d B. The experimental results also demonstrate that the use of such reverse-active device does not impose any performance degradation, particularly in terms of linearity