A systematic method is given for generating negative-resistance circuits made of 2 transistors and linear positive resistors only. The 2 transistors may be bioolar (n-p-norp-n-p),JFET(n-channel or p-channel),MOSFET(n-channel orp-channel), or their combinations. Since the circuits do not require an internal power supply, they are passive and can be integrated as a two-terminal device in monolithic form. Two algorithms are given for generating a negative-resistance device which exhibits either a type-Nupsilon - icharacteristic similar to that of a tunnel diode, or a type-Supsilon -icharacteristic similar to that of a four-layeredp-n-p-ndiode. Hundreds of new and potentially useful negative resistance devices have been discovered. A selected catalog of many such prototype negative-resistance devices is included for future applications.