single-chip AF power amplifier
single-chip AF power amplifier
If you’re looking for an audioamplifier that produces a lot ofpower using an absolute minimumnumber of components,this one is for you.Burr-Brown’s OPA541 is apower opamp capable of operationfrom power supplies up to}40 V and delivering continuousoutput currents of up to5 A. Internal current limit circuitrycan be user-programmedwith a single external resistor,protecting the amplifier and theload from fault conditions. TheOPA541 is available in an 11-pin power plastic package andan industry-standard TO-3 hermeticpackage. The former isused here.
Although the OPA541 isprimarily intended for applicationslike motor drivers, servoamplifiers and programablepower supplies (says B-B), it isalso fine for a medium-powerAF amplifier with reasonablespecifications. The designshown here is capable of supplyingabout 60 watts into an 8-Ω load.
This is achieved with anaudio drive level of 1.3Vrms anda symmetrical supply voltage of}35 V. The on-chip currentlimiter is set to an actuationlevel of about 8.5 A by parallelconnectedresistors R6/R7. Thislevel ensures that the maximumdrive margin can also beachieved with a load of 4 Ω.Note, however, that R6 and R7do not make the amplifiershort-circuit proof, because thatwould require a current limiterthreshold of 1.8 A, assumingthat the IC is operated withinits SOA (safe operating area,for details consult the B-Bdatasheets).