COMPLEMENTARY 2-TRANSISTOR CIRCUITS AND NEGATIVE DIFFERENTIAL RESISTANCE

We consider the dc behavior of nonlinear one-ports employing two complementary Ebers-Moll modeled transistors and no internal independent sources. We prove that, in the absence of internal resistors, all such one-ports—irrespective of their internal topology and transistor parameter values—cannot exhibit negative differential resistance (NDR) for any value jof an external biasing current source. One well-known circuit employing two complementary transistors and no resistors is of particular interest, since it is often cited as a two-transistor simplified model for SCR devices. Our results thus demonstrate that either the transistor behavior unaccounted for in an Ebers-Moll type model must be involved in this one-port’s NDR behavior, or else the presence of internal resistors is essential to such a circuit’s behavior having even a generally correct qualitative character. © 1990 IEEE