B-Terminal strip construction-Custom Design
Circuit Board Electronic Pcb
Terminal strip construction
Some audiophile equipment, such as amplifiers, continues to be point-to-point wired using terminal pins, often in very small quantities. Point-to-point wiring is used as a design feature rather than a result of the economics of very-small-scale production.
Sometimes true point-to-point wiring—without terminal strips—with very short connections, is used at very high radio frequencies (in the gigahertz range) to minimise stray capacitance and inductance; the capacitance between a circuit-board trace and some other conductor, and the inductance of a short track, become significant or dominant at high frequencies. In some cases careful PCB layout on a substrate with good high-frequency properties (e.g., ceramic) is sufficient. An example of this design is illustrated in an application note describing an avalanche transistor-based generator of pulses with risetime of a fraction of a nanosecond; the (few) critical components are connected directly to each other and to the output connector with the shortest possible leads.
Particularly in complex equipment, wired circuits are often laid out as a "ladder" of side-by-side components, which need connecting to ladders or components by wire links. A good layout minimizes such links and wiring complexity, often approaching that of direct point-to-point. Amongst complex devices, the pre-PCB Tektronix vacuum-tube oscilloscopes stand out for their very well-designed point-to-point wiring.
If parasitic effects are significant, point-to-point and terminal strip wiring have the disadvantage compared to a PCB of indeterminate parasitic components; while the inductance and capacitance due to a PCB are the same for all samples, values may vary between point-to-point wired units, changing circuit operation.
Placing the completed unit in an enclosure protects the circuit from its environment, and users from electrical hazards.
A few large brand names still use terminal strip-type point-to-point boards, but usually for special product lines. Electric guitar amplifier manufacturer Marshall have reissued some of their older models, using this type of construction as a design feature, although their standard products have long used PCBs. Thermionic valve equipment usually does not have the valves mounted on the PCB in order to avoid heat damage, but instead use PCBs for the wiring, achieving the economy of mass-produced PCBs without the heat damage.
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