A two-stage amplifier where the two transistors or vacuum tubes are connected in series in such a way as to force the voltage gain of the first active device to be unity. This connection minimizes the input capacitance of the amplifier by eliminating the Miller effect, which would otherwise multiply the influence of the internal feedback capacitance of the first device by its voltage gain. Wide-bandwidth amplification and high-speed switching can therefore be achieved.

Typical configurations include a common-emitter amplifier loaded by a common-base amplifier, using bipolar transistors, and a common-cathode amplifier loaded by a common-gate amplifier, using vacuum tubes. In each case, the current gain of the second active device is unity, but the overall power gain of the pair of devices is comparable to that of a single device due to current gain in the first stage and voltage gain in the second stage; this performance is maintained up to the transition frequency of the transistors.