405 audio ics 6v / 330mw single-channel power amplifier BA546 the BA546 is a monolithic power amplifier designed for use in portable radios, tape recorders and interphones. with a 6v power supply voltage, it has a rated output of 330mw into an 8 w load (thd = 10%), and a maximum output of 550mw. it comes in a compact 9-pin sip package with no heatsink fins. applications portable radios, cassette recorders, and interphones. features 1) high output. pout = 330mw (v cc = 6v and an 8 w load (thd = 10%)). see fig. 2. 2) good low voltage characteristics. begins operating at less than 2v (see fig. 1). 3) 9-pin sip package; around the same size as a pre- amplifier. 4) pin compatible with the rohm ba526 and ba527 power ics. choose to suit your application. 5) low current dissipation (4.8ma typ.). block diagram
406 audio ics BA546 internal circuit configuration absolute maximum ratings (ta = 25 c) electrical characteristics (unless otherwise noted, ta = 25c, v cc = 6v, r l = 8 w and f = 1khz)
1 f lc1 = 2 p c 1 r in [hz] 1 f lc2 = 2 p c 2 r nf [hz] 4000 f hc = c4 [pf] [khz] 407 audio ics BA546 measurement circuit attached components (see fig. 1) c 1 : input coupling capacitor the recommended value is 10 m f. this capacitor and r in determine the bass cutoff frequency f lc1 for the input stage according to the following formula: if the capacitance value of c 1 is too small, the signal source reactance will increase, and cause the noise to increase and f lc1 will become higher. conversely, if it is too large, the startup time after power is ap- plied will be longer, and if the potentiometer is ad- justed while the capacitor is charging, the charging current will flow through the slider current, and cause noise. c 2 : dc cutoff resistor for the feedback circuit the recommended value is 47 m f. this capacitor and r nf determine feedback circuit bass cutoff fre- quency f lc2 . f lc2 is given by the following formula: fig. 7 illustrates how changing c 2 varies the bass characteristics. c 3 : ripple filter capacitor the recommended value is 47 m f. c 4 : phase compensation capacitor this capacitor determines the treble cutoff frequen- cy f hc . f hc is given by the following formula: (however, g vc = 50db) if g vc is not 50db, f hc doubles for each decrease in g vc of 6db. fig. 7 illustrates how changing c 4 varies the treble characteristics. c 5 : ripple filter and pre-driver bypass capacitor the recommended value is 100 m f. if this capacitor is made too small, the ripple rejection and power output will deteriorate. c 6 : output coupling capacitor the recommended value is 470 m f. c 7 : power supply filter capacitor determine based on the amount of power supply ripple and the regulation.
24k w g vc 20log r nf [db] 408 audio ics BA546 circuit construction (see fig. 2) (1) voltage amplification stage this circuit is comprised of a differential amplifier (q 1 and q 4 ), a constant current source (q 5 ), and an active load (q 2 and q 3 ). this active load is the input to the pre-driver (via q 8 and q 9 ). (2) pre-driver the pre-driver is an earthed-emitter amplifier with tran- sistors q 8 and q 9 forming a darlington pnp transistor. the q 9 collector load is the input impedance looking from the base of q 14 and the constant-current load due to q 12 . (3) idling loop the idling loop is the q 13 , q 10 , q 11 and q 14 loop. the v be of q 13 is subtracted from the v f of q 10 and q 11 and is biased by q 14 . (4) power stage the power stage is a quasi-complementary circuit made up of a darlington pnp transistor (q 13 and q 15 ), and an npn transistor (q 14 ). (5) the ac gain is determined by the ratio between r 6 (24k w ) and r nf connected to pin 7. the formula is as fol- lows: variation of g vc and thd with r nf is shown in fig. 12. application example the BA546 will generally be used as a power amplifier for portable cassette players and similar equipment, and will usually have a preamplifier before it, so insert the volume control between the stages. the gain of the power stage alone is determined by r nf . use fig. 12 to choose a value for r nf that gives the required gain. when r nf is 68 w , the standard g vc is 50db. when com- bining the BA546 with an alc-equipped preamplifier as the previous stage, the control voltage for the alc can be taken from pin 4, and the power supply for the pream- plifier from pin 9.
409 audio ics BA546 electrical characteristics curves
external dimensions (units: mm) 410 audio ics BA546
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