Feature: Electronic design


Figure 11: The output impedance of the cascode TIS of Figure 10 is roughly 164Kohms at 20Hz with single-pole minor negative feedback loop compensation, which is more than 440 times the output impedance of Q8 in Figure 1 at the same frequency


Figure 12: The first pair of complementary emitter-follower drivers Q12 and Q13 in this triple output stage operate in Class A, provided their emitter-coupling resistor R18 is sufficiently small. This improves the isolation of a cascode TIS from the non-linear loading of the output stage


Figure 13: In this arrangement, the novel differential boosted-current complementary folded cascode TIS’s differential pairs are bypassed by feed-forward capacitors C2 and C3, which at high frequencies drive the TIS’s current mirrors directly. This drastically improves the minor negative-feedback loop’s stability margins


www.electronicsworld.co.uk December 2021/January 2022 53


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