David Magliocco

A simple circuit can improve the dynamic performance of a phototransistor for use in low- to medium-speed applications as fast as 100 kbps, such as optical isolation of an RS-232C serial line (Figure 1). In low-cost applications that require high voltage insulation,...

You can use simple circuits to implement small, regulated plug-in power supplies. In Figure 1, a basic and versatile 5 V supply uses a zener diode and an emitter-follower transistor. You must calculate and design the transformer such that Q1 is close to saturation at...

The circuit in Figure 1, using a low-offset amplifier, is a basic ohmmeter circuit common in multimeters, except for the addition of the two diode-connected transistors. A current source supplies a selectable current, IM, to ranging from 100 nA to 1 mA to RX. An...