Simple diodes

Likewise, a p-type material is best doped with atoms that produce empty states near the valence band edge and having a low chemical potential for electrons. When these two materials are brought into contact, electrons are free to move. 

The large electron concentration gradient across the junction causes electrons to diffuse from the n-type to the p-type side, leaving positively-charged donor dopant 

---

A fluorescence spectrometer (Fig. 11.27) typically uses an input monochromator (with prism or grating) to select one particular frequency for the input light beam, and then it uses an output monochromator (also with prism or grating) to monitor the emission wavelength. If one uses a multichannel analyzer instead of a simple diode detector, then the output monochromator is not needed. 

Schematic representation of a simple diode type ion plating system.

Figure 4.57 Idealized layout for a simple diode array-based spectrograph. (From Coates, used with permission.)...

When narrow fine fight sources are used, a scanning monochromator is largely redundant, so an interference filter will be sufficient, e.g., to isolate one mercury lamp emission fine or one fine from multiline laser such as an argon-ion laser. Single-line lasers such as simple diode lasers need no filter or monochromator at all in the excitation beam. 

If a diode s source of power is an alternating emf, electrons can flow during only half the cycle. A simple diode with a single-phase AC supply voltage produces a series of half-waves separated by half-cycle intervals. A three-phase signal has no periods without current flow but is still extremely choppy. Adding a second element shifted 180° in phase from the first, for example in a second wye connection with reversed polarity, fills the gaps and produces full-wave rectification. 

Anofiier advantage of thyristors over simple diodes is their faster control action. This gives more protection against transient surges in current. Control still requires completion of an electrical cycle before the supply can be interrupted. Response time is measured in tens of milliseconds. Therefore, thyristors are not able to eliminate very... 

With a simple diode receiver such as the one we will build, the bottom half of the radio wave is lost. With a more complex receiver, there usually are two transistors doing the job of detection, instead of just a single diode, and one of these could operate on the bottom half of the signal. This provides better use of the radio wave s energy. 

Complex analog devices such as analog or mixed-signal ICs are not very amenable to analog in-circuit testing because they require power to be apphed to the board. Simple diodes and single transistors can be tested by in-circuit stimulus that essentially examines the characteristics of their semiconductor junctions. 

---