A previous Design Idea describes a circuit that uses an astable multivibrator to drive an LED (Reference 1). The circuit in Figure 1 uses a simpler alternative approach. The circuit uses a 2N3904 NPN ...

Wanting an auto-off circuit simple electronics, [Kyle] threw together this auto shutoff circuit. ... This pin feeds into a PNP transistor which is in turn connected to a NPN transistor, ...

In the simple circuit shown in Figure 9.9 (the case shown is for an NPN transistor, but a virtually identical circuit, but with negative supply rails, could be made with a similar PNP transistor), the ...

A very simple but highly efficient combination lock circuit ... A very simple but ... S5, S8, S9, and S10). These switches need to be "ON" (binary state "1") to forward-bias the transistor ...

The circuit in the figure shows a low-cost solution based on a transistor switch (Q1). The transistor is off under normal conditions, when the differential amplifier built around U1 amplifies the ...

A more practical optical transistor debuted in April 2012 at Purdue University in West Lafayette, Indiana, where electrical engineer Minghao Qi has made one that is compatible with the ...