By Paul M. Brown Jr.
Program particular built-in circuits (ASICs), either analog and electronic, became regular approach point bulding blocks. ASIC owners have tried to supply instruments that they wish will permit really green IC designers (i.e. platforms engineers) to layout refined customized built-in circuits. This philosophy has been extra profitable in electronic expertise than in analog. considerably extra paintings is concerned with analog layout and much fewer automated instruments can be found. nearly each analog ASIC seller bargains varied semiconductor applied sciences, device units, documentation (usually missing intimately and never delivering the correct heritage and guidelines), and ranging degrees of engineering aid. the result's that many engineers who may well use analog ASICs lack the technical details to take action. they don't seem to be definite whilst customized analog ICs are within your means or which seller will most sensible serve their wishes. furthermore, many engineers should not have sufficient analog layout adventure, specially with built-in circuits. Consqeuently, many that may benefit from analog ASIC know-how don't use it whereas others have undesirable studies which may have simply been kept away from.
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Additional info for A Guide to Analog Asics
The model elements will then be related to the structure of the device. This will help to cement the concepts of the model with the physical structure of the device and lay the groundwork for SPICE modeling in Chapter 4 and circuit design concepts in Chapter 5. JFET Model The JFET is a depletion-mode device (it is on until turned off) and be haves like a voltage-controlled resistor. The ends of the "resistor" (channel) are referred to as the source and drain and are interchange able. The control element is referred to as the gate.
5 Junction Field-Effect Transistors Ion-implanted p-channel junction field-effect transistors, JFETs, are the newest active devices to be added to bipolar analog semicustom arrays. The JFETs available on semicustom arrays, however, are usually fairly small-geometry devices (relatively high R , and low I s s ) . They are very similar to ion-implanted resistors except an η-type implantation is made over the ρ implantation to serve as the top gate of the JFET. Figure 3-19 illustrates a typical JFET geometry found on semicustom arrays.
IC manu facturers change their processes from time to time to improve perfor mance and production yields. If you are considering multiple sources for a custom IC, it is wise to review the design data from the alternate manufacturer(s) prior to beginning detailed design work. A little re search up front will help you identify and avoid vendor dependencies. This forethought will guarantee you a design that is sourceable with high production yields from multiple vendors. Integrated circuit components found on semicustom arrays, al though very similar to the common discrete components for which they are named, have several unique characteristics.