This means that a Sziklai output stage in a class AB amplifier requires only that the bias servo transistor or diodes be thermally matched to the lower power driver transistors; they need not (and should not) be placed on the main heatsink. This potentially simplifies the design and implementation of a stable class AB amplifier, reducing the need for emitter resistors, significantly reducing the number of components which must be in thermal contact with the heatsink and reducing the likelihood of thermal runaway. Optimal quiescent current in an amplifier using complementary feedback pairs also tends to be much lower than in Darlington-based output stages, on the order of 10mA vs. 100mA or more for some emitter follower output stages. This means that idle power consumption is on the order of a few watts versus tens of watts for the same performance in many cases. This is a very compelling reason to use the Sziklai pair in cases where output power is moderate (25-100W), fidelity is critical and relatively low idle power consumption is desired. Historically, designers frequently used the "quasi-complementary" configuration, which uses a Darlington push pair (i.e., two NPN transistors) and a complementary feedback pull pair (i.e., one PNP and one NPN transistor). This configuration, which uses three NPN transistors and one PNP transistor, is advantageous because while the first transistors and the most common small signal transistors for decades were PNP germanium devices, silicon PNP power transistors were slower to develop, and have historically been more expensive, than their NPN counterparts. Alternately, if a germanium PNP device were used, it would have significantly different characteristics. In the quasi-complementary topology, the performance of the lower pull pair, which used a single NPN transistor, more closely matched the performance of the upper push pair, which consists of two NPN transistors and an identical power device. While for decades the quasi-complementary output stage made sense, since PNP and NPN power transistors became roughly equally available and had more closely matched performance characteristics, modern audio power amplifiers often use equivalent topologies for both pairs; either both Darlington emitter follower or both Sziklai pair.