This circuit was designed to meet a medical application’s requirement to drive a laser diode with reasonable precision and a minimum of components and footprint (the device is now in clinical trials).

The top circuit, in the diagram above, is a half-wave rectifier and you can see the circuit’s effects on a sinusoidal signal. What is the bottom circuit and how would it effect a sinusoidal input?

This circuit was designed to meet a medical application’s requirement to drive a laser diode with reasonable precision and a minimum of components and footprint (the device is now in clinical trials).

The Design Idea in Figure 1 indicates a low-battery condition in an audio test instrument that is powered by four AA cells. As the instrument was otherwise an all-discrete design, this same approach ...