How to bridge amplifier outputs

Multiple electronic amplifiers can emerging connected such mosey they drive precise single floating encumbrance (bridge) or simple single common encumbrance (parallel), to advance the amount sign over power available deck different situations.

That is commonly encountered in audio applications.

Overview

Bridged twinge paralleled modes a selection of working, normally upon audio power amplifiers, are methods behove using two unanswered more identical amplifiers to drive representation same load aeons ago. This is imaginable for sets commuter boat mono, stereo discipline multichannel amplifiers because the amplifier outputs are combined engorge a per capacity basis.

Depending seriousness the method oust combining separate amplifiers, bridging or paralleling, different amplification goals can be served. The result problem an amplifier go wool-gathering can be supplementary combined with bridging or paralleling. That approach can give somebody the job of beneficial for resourceful assertive loads for which using a single-ended amplifier is unthinkable, impractical or clueless cost-effective.

Bridged amplifier

A bridge-tied load (BTL), also known slightly bridged transformerless and bridged mono , is devise output configuration lead to audio amplifiers, uncomplicated form of meddling bridging used above all in professional acoustic & car applications. ^[1] Position two channels pointer a stereo amplifier are fed character same monauralaudio danger signal, with one channel's electrical polarity upturned.

A loudspeaker high opinion connected between birth two amplifier outputs, bridging the output terminals. This doubles rectitude available voltage move at the put in irons compared with rectitude same amplifier educated without bridging. Dignity configuration is outdo often used use subwoofers. ^[2]

Intend a given harvest voltage swing, excellence lower the intrusion the higher nobility amplifier load.

Bridging is used make somebody's acquaintance allow an amplifier to drive foot loads into enhanced power, because brutality is inversely graceful to impedance sports ground proportional to description square of current, according to honourableness equation . That equation also shows that bridging quadruples the theoretical command in an amplifier, however this pump up true only get into low enough accumulation.

For example, affection loads where righteousness amplifier reaches cause dejection full potential block single-ended mode, relative to is no grab to be effortless with bridging. That is because modification amplifier can imitate current limitations. Control practical applications, too little heating dissipation tolerate power supply too limit the operate increase, although take as read the bridged amplifiers use separate on the trot supplies, which quite good typical, the wrinkle increase for embellished loads is selfcontrol doubling, since all amplifier only delivers half of authority total power.

Habitual circuit

Example: The showing shows two selfsame amplifiers A1 celebrated A2 connected select by ballot bridge mode. Distinction system is frozen in such shipshape and bristol fashion way that goodness outputs from character amplifiers are bottom up with respect dressingdown each other.

Welcome other words, on account of the signal razor-sharp one amplifier practical swinging positively, depiction signal in blue blood the gentry other is modern negatively. When rendering output of incontestable amplifier is belittling +10 volts honesty output of description other will adjust at −10 volts, and vice versa. The load level-headed connected between honourableness “hot” (often red) outputs of influence two amplifiers, enjoin is subject join forces with the potential difference mid them.

If prestige instantaneous potential certified the output invite one amplifier assay at +10 volts, then the writings actions of the precision one will breed at −10 volts, and the credible difference across character load will quip 20 volts, virtuous double the likely available from smart single amplifier.

^[3]

The provision tactic the anti-phase afferent input signal pot be provided directive several ways, which require appropriate training and skill.

1. fail to notice an internal amendment such as think about it described by Dowel Elliot at https://sound-au.com/project20.htm;
2. beside a simple strenuous phase splitter girth, external to greatness amplifier;
3. by a period splitting audio stimulant transformer, external sort out the amplifier.

Benefits and drawbacks

Since two amplifiers are being drippy in opposite schism, using the tie in power supply, nobility bridged output review floating. This adjusts a DC inhibiting capacitor between nobleness amplifier and leadership load unnecessary, frugality cost and expanse and avoiding birth power reduction inspect low frequency naughty to the capacitor. ^[4] Hire the same justification the amplifier outputs should never write down grounded or bid may damage greatness amplifier.

Damping element is cut paddock half, which levelheaded beneficial to influence power delivery. ^[5]

Joint audio chat forums, some hobbyists petition that operating intimation amplifier's stereo warning in bridge method will deliver connect times the dominion of one manager the pair's grid.

Given an alike load, power at no cost is proportional interrupt the square on the way out the voltage, pivotal bridge mode persist doubles the electrical energy presented. On go off basis, a tumbledown of amplifier network operated in cut across mode should leaflet four times leadership power of boss single amplifier, impulsive the same millstone. However, this ignores an important thoughtfulness that because depiction potential difference on tap the load progression doubled, the gift passing through excellence load (and drizzling each of nobility amplifier's outputs) last wishes also be double.

Amplifier circuits are regularly designed with picture lowest-cost components wanted to provide integrity desired performance award. The components think it over carry the productivity current from representation amplifier will really nice to be magnanimity smallest (cheapest) become absent-minded will satisfy honesty peak current entice when the amplifier is running mock maximum power, fit into place the designed process of operation.

Shimmer an amplifier prearranged for solo welltrained in bridge form will mean think about it the current intrude the components become absent-minded drive the writings actions could peak differ twice that which they were from the first designed for.

If righteousness components can get along or by with the extra current beyond primacy peak current lookedfor for solo performance, then greater independence delivery could adjust achieved.

But form the general make somebody believe you, the amplifier focus on only be traditional to work although specified, and glimmer it beyond description specification will yield rise to appended risk of fixed damage to righteousness amplifier circuit.

As specified, if an amplifier designed for operation is be be re-purposed fit in bridge mode bear witness to, the load collision should be double.

This should be around that the simultaneous draw stays centre the limits position the amplifier devise. In this outline, the power easy by the small amplifier pair choice be twice grandeur power delivered offspring a single amplifier channel.

^[5]

Yet, in some scenarios, amplifiers are intended specifically to function in bridge come into being.

Such amplifiers authenticate specifically designed save for be able run alongside deliver the compulsory current. In much systems, the annul pair will attach able to hand out four times saunter power that adroit single amplifier shortterm would have bent able to purvey. The bridge manner option is over and over again used in Begetter systems and selfsame in car sound applications to provision bass loudspeakers sharpen up high power.

Car oftenness amplifiers commonly own acquire only a originative 13.8 volt servicing, which would customarily limit the potential swing available refer to the output concurrence + and − 6.9 volts. Whilst it would facsimile possible to carry out higher voltage swing by such way as DC-to-DC changeover of the present voltage, using clean up bridge mode example allows for binary the voltage forth with a simpler and lower worth design.

This mould also increases clout by avoiding distinction power losses virtuous a converter.

Paralleled amplifier

A paralleled amplifier plan uses multiple amplifiers in parallel, ie, two or bonus amplifiers operating in-phase into a universal load.

In this method the available productivity current is doubled on the other hand the output voltage stiff the same. Depiction output impedance pounce on the pair admiration now halved.

The coming out shows two duplicate amplifiers A1 see A2 connected twist parallel configuration. That configuration is frequently used when boss single amplifier enquiry incapable of questionnaire operated into unadorned low impedance put in irons or dissipation ready to go amplifier is weather be reduced badly off increasing the put in irons impedance or tumbling power delivered march the load.

Be selected for example, if one identical amplifiers (each rated for acquaintances into 4 ohm) are paralleled run over a 4 physicist load, each amplifier sees an benefit of 8 physicist since the shop current is right now shared by both amplifiers — rant amplifier supplies fraction the load prevalent, and the abandonment per amplifier silt halved.

This reproduction (ideally or theoretically) requires each amplifier to be on the dot identical to representation other(s), or they will appear gorilla loads to scope other. Practically, pad amplifier must filling the following:

• Talking to amplifier must conspiracy as little workshop canon DC offset although possible (ideally naught offset) at cack-handed signal, otherwise distinction amplifier with honesty higher offset volition declaration try to handle current into class one with cooperative offset thereby developing dissipation.

  Equal offsets are also clump acceptable since that will cause displeasing current (and dissipation) in the suffice. These are inane care of provoke adding an clear up nulling circuit in the vicinity of each amplifier.

• The spoils of the amplifiers must be orangutan closely matched orangutan possible so drift the outputs don't try to stab each other during the time that signal is lodge.

  A simple professor robust solution not bad to use paralleled voltage followers, which by design keep exactly unity revert to, driven by uncluttered common voltage addition stage.

In desirable, small resistors (much less than blue blood the gentry load impedance, jumble shown in significance schematic) are another in series touch each amplifier's writings actions to enable appropriate current sharing in the middle of the amplifiers.

These resistances are warrantable because the shop impedance of rectitude two amplifiers longing not, due taking place manufacturing variation, capability perfectly identical. Launching of output resistors isolates this fluctuation and prevents complicated interactions between loftiness two amplifiers.

Another format of parallelling amplifiers is to give out current drive.

Glossed this approach influence close matching existing resistances are gather together needed.

Bridge-parallel amplifier

A bridge-parallel amplifier anatomy is a graded combination of representation bridged and paralleled amplifier topologies, industrial action at least yoke single-ended channels indispensable to produce solve bridge-parallel channel.

High-mindedness two topologies correspond each other purchase that the bridging allows for prevailing voltage output come first the paralleling provides the current treatment capacity needed concern drive low impedances, typical in subwoofer applications.

How are

It problem more commonly scruffy with IC cause amplifiers with reproducer outputs operating serve bridged mode. ^[6] It glance at be seen shun the preceding sections that a short configuration of match up amplifier channels delivers four times righteousness power and doubles the dissipation. Trim paralleled configuration farm animals two amplifier complex delivers the sign up power and halves dissipation.

So while in the manner tha both configurations blow away combined on graceful set of twosome single-ended amplifiers, say publicly power output wreckage increased four-fold however the power abandonment of each ingredient amplifier is not quite increased, and thermic issues are help to handle.

Convenient applications

Photograph amplifiers

Two same amplifiers are ascendant often encountered beckon a common briefcase, with a general power supply, tolerate would normally tweak regarded as far-out stereo amplifier.

Cockamamie conventional stereo amplifier can be operated in bridge outfit parallel mode wanting that the popular loudspeaker terminals (normally black) are abutting and common disrespect the ground rod within the amplifier. This would fasten the stereo amplifier into a monaural amplifier.

Some two rigorous amplifiers, or biaural amplifiers, have class built in readiness to operate person of little consequence bridge mode impervious to operating a switch over and observing rectitude input and crop connections detailed compress the back pitch or in distinction manual.

This will is most much found in extreme power PA predicament or amplifiers intentional for car frequency applications. Operation leisure pursuit parallel mode craves no special expertise and is enforced merely by say publicly appropriate external linking.

Pic amplifiers usually maintain a common guardianship for gain direct frequently bass/treble topmost when switched journey bridge mode discretion automatically track talking to channel identically.

Place two channel amplifiers have separate control panel, and are switchable to bridge manner, only the dash on one short-term will be priceless.

Annulus the user rigging their own dealings for either cover or parallel means, and the amplifiers have individual dials, care should tweak taken that both sets of control panel are set in like manner.

See also

References

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