ba3308 / BA3308F audio ics 1/8 dual preamplifier with alc ba3308 / BA3308F the ba3308 and BA3308F are dual preamplifier ics with built-in alc circuits, and have been designed for use in stereo radio-cassette recorders and tape recorders. they come in compact 9-pin sip (ba3308) and 14-pin mf (BA3308F) packages, and have two record / playback preamplifiers, and an alc circuit. the preamplifiers have high gain and low distortion, and can be directly coupled to the tape head without coupling capacitors. this prevents tape head magnetization and ?pop? noise generation. a built-in rectifier means that an alc circuit with good channel balance and large dynamic range can be constructed with addition of just an external time constant circuit. the ics also include power-on mute circuits that suppress ?pop? noise generation. ! ! ! ! applications stereo radio cassette recorders, cassette decks and home stereo systems and music centers ! ! ! ! features 1) built-in alc rectifier diode. 2) wide operating power supply voltage range (v cc =6.0v to 14v) 3) low current dissipation (i q =3.5mv) 4) high gain (g vo =80db) 5) low distortion (thd=0.1%) 6) low noise (v nin =1 vrms) 7) input coupling capacitors and not necessary. 8) good alc channel balance. 9) power-on mute circuit. 10) alc dynamic range can be varied by the addition of an external input resistor. ! ! ! ! absolute maximum ratings (ta=25 c) parameter symbol limits unit v cc 16 v ba3308 pd 950 ? 1 ? 2 mw BA3308F 450 topr ? 25 to + 75 c tstg ? 55 to + 125 c power supply voltage power dissipation operating temperature storage temperature ? 1 reduced by 9.5mw for each increase in ta of 1 c over 25 c. ? 2 reduced by 4.5mw for each increase in ta of 1 c over 25 c (when mounted on a 70mm 70mm 1.6mm glass epoxy board). ! ! ! ! recommended operating conditions (ta=25 c) power supply voltage parameter symbol min. typ. max. unit v cc 6.0 ? 14 v
ba3308 / BA3308F audio ics 2/8 ! ! ! ! block diagram 123456789 alc mute ch1 + ? ch2 ? + nf1 input1 output1 gnd alc v cc output2 input2 nf2 alc v cc 1 2 3 4 5 6 7 14 13 12 11 10 9 8 + + ? ? n.c. n.c. n.c. n.c. n.c. ba3308 BA3308F ! ! ! ! electrical characteristics (unless otherwise noted, ta=25 c, v cc =7.0v, f=1khz and bpf: 20hz 20khz) parameter symbol min. typ. max. unit conditions i q 1.5 3.5 4.5 ma v in = 0vrms g vo 70 80 ? db v out =? 10dbv thd ? 0.1 0.3 % nab34db, v out = 40mvrms r in 15 25 45 k ?? v om 0.6 1.2 ? vrms thd = 1% v nin ? 1.0 2.0 vrms alc 40 45 ? db ? alc ? 0 2.5 db v in =? 60dbv, ? 30dbv cs 60 75 ? db v o = 0dbv, nab34db quiescent current open loop voltage gain total harmonic distortion input resistance maximum output voltage input conversion noise voltage alc range alc channel balance channel separation conversion with r g = 2.2k ? and nab34db at 1khz r g = 3.9k ? , v in =? 70dbv reference, thd = 3%
ba3308 / BA3308F audio ics 3/8 ! ! ! ! measurement circuit fig. 1 123456789 ch2 ba3308 ch1 alc mute v sw1a 3 2 1 2.2k ? sw6a sw4a 3.9k ? 10k ? 30k ? 120k ? 1.2k ? 33k ? 39 ? 100 f 10 f output1 input1 0.1 f sw3a sw3b 0.1 f input1 output2 10 f 100 f 39 ? 33k ? 1.2k ? 120k ? 30k ? 10k ? 3.9k ? sw4b sw6b 2.2k ? 1 2 3 sw1b sw2b 1 2 1 2 330 f 22 f 220 ? 1m ? sw5 v cc sw2a v 2 v 2 v 1 v ~ v 1 v ~ v ~ v ~ v ~ ! ! ! ! application example ! ! ! ! application example circuit pcb (copper side) fig. 2 123456789 alc mute ch2 ch1 ba3308 4.3k ? 120k ? 39 ? 18k ? 18k ? 220 ? 3.9k ? 39 ? 3.9k ? 1m ? 0.027 f 100 f 10 f 10 f 22 f 330 f 10 f 10 f 100 f 7v output2 input2 input1 output1 r 5 r 3 c 3 r 1 c 5 c 5 r 7 c 7 c 8 c 6 r 6 c 2 c 4 r 4 r 8 v cc r 2 r 9 (r 10 ) r 11 (r 12 ) c 9 (r 10 ) for playback, instead of r 5 and r 6 , connect the following nab time constant circuit between pins 1 and 3 and 7 and 9. ba3308 1pin (40 60mm) fig.3
ba3308 / BA3308F audio ics 4/8 ! ! ! ! total application circuit fig. 4 ba3308 ba5406 mic radio etc. 3.9k ? 3.9k ? 220 ? 39 ? 120k ? 4.3k ? 18k ? 100 f 330 f 0.027 f 2 8 1 6 3 7 5 4 9 l 5 8 4 1 7 3 2 11 6 12 9 2.2 f 2.2 f 33 f 100 f 47 f 1000 f 10k ? 10k ? 120 ? 10 f 10 f 10 9v 0.027 f 100 f 39 ? 22 f 1m ? 18k ? 120k ? 4.3k ? l bias osc 120 ? 33 f 47 f 47 f 0.22 f 0.22 f 470 f 470 f 2.2 ? 2.2 ? sp 3 ? sp 3 ? c c c a r a c b c b r a c a c c notes: (1) switches are in the playback positions. (2) set the values of r a and c a depending on the characteristics of the playback/recording head. (3) the capacitor c b is for head resonance treble compensation during playback, and prevention of high-frequency noise. the recommended value is about 1000pf. (4) l and c c are a bias trap. ! ! ! ! circuit operation (1) recording 1) recording amplifier (see fig.5) the channel 1 and 2 amplifier input stages of the ba3308 (pins 8 and 2) and be direct-coupled, and the input coupling capacitors c 1 and c 2 are not particularly required. the voltage gain of the recording amplifier is given by g v = r 5 / r 3 , but as a ?pop? noise is generated when power is applied, (see ?operation notes?), use the time constant circuit values given for c 3 and r 3 (c 4 and r 4 ) in the application example circuit diagram, or values close to these, and adjust the voltage gain with r 5 (r 6 ). r 5 (r 6 ) is also the dc bias feedback resistor, and is connected between pin 3 (7), and the output capacitor c 5 (c 6 ). 2) alc (see fig.6) the ba3308 includes a signal rectifier block and electronic potentiometers required for the alc. in the signal rectifier block, a comparator compares the dc output voltage component of the output stage signal (pins 3 and 7) to a voltage of 4.5v f (1v f is about 0.7v, so 4.5v f is approximately 3v), and if it is above this, the comparator switches on, and changes the smoothing capacitor c 7 . the operating point of the amplifier?s ch1 and ch2 output stages is fixed at 3v f , so when the signal output voltage is 1.5v f (an effective value of approximately 0.75v), the comparator goes on, dc signals for electronic potentiometer control are generated, and the alc starts operating. the electronic potentiometers are connected between the input lines (pins 2 and 8) and gnd, and the input signals is attenuated by the ratio of the electronic potentiometer resistances and the external resistors r 1 and r 2 . the range of the alc can be varied by the values of r 1 and r 2 , but if they are too large the s/n ratio will worsen. sufficient alc range should be obtained with r 1 and r 2 values of around several k ohms. c 7 and r 7 connected to pin 5 set the alc attack and recovery times. the larger the values of these constants, the longer the recovery time, and the smaller the value of c 7 the shorter the attack time.
ba3308 / BA3308F audio ics 5/8 (2) playback (see fig.7) during playback, the ch1 and ch2 amplifiers are used as nab equalizer amplifiers, and time constant circuits are connected between pins 1 and 3, and 7 and 9 in the negative-feedback section to give the nab characteristics. the voltage gain is given by: g v = | r 11 + r 9 / (i + j c 9 ? r 9 ) | / r 3 in the same way as for recording, the nab time constant circuit is adjusted to give the required gain (to prevent generation of a ?pop? noise when power is applied). the output stage (pins 3 and 7) operating point is fixed at 3v f . therefore, as indicated in the v max. vs, v cc characteristic (see fig.19), even if the v cc voltage is made larger than 5v, the maximum output voltage will not exceed 1.2v (typ.). the alc circuit is not required for playback, so pin 5 is grounded. the s/n ratio during playback is better if the external resistors r 1 and r 2 that are connected to the input pins (2 and 8) for recording are switched out. fig.5 ba3308 cont ch2 (ch1) ch2 (ch1) ch1 (ch2) 2 (8) 1 (9) 3 (7) 5 3.9k ? 10 f input 39 ? 18k ? 1m ? 100 f 10 f 22 f output r 1 (r 2 ) r 3 (r 4 ) r 5 (r 6 ) r 7 (r 8 ) c 1 (c 2 ) c 3 (c 4 ) c 5 (c 6 ) c 7 (c 8 ) fig.6 ch2 (ch1) ch2 (ch1) ch1 (ch2) cont comp ba3308 3 (7) 5 2 (8) 4.5v f v out (dc + ac) 3v f r 7 c 7 r 1 (r 2 )
ba3308 / BA3308F audio ics 6/8 fig.7 a1 ba3308 2 (8) 10 f 100 f 10 f 0.027 f 39 ? 4.3k ? 120k ? 1 (9) 3 (7) 5 input output r 9 (r 10 ) r 11 (r 12 ) r 3 (r 4 ) c 5 (c 6 ) c 9 (c 10 ) c 3 (c 4 ) c 1 (c 2 ) ! ! ! ! operation notes the ba3308 has a built-in power-on mute circuit to prevent generation of a ?pop? sound when the power is applied. the generation of the ?pop? sound is prevented by the dc blocking capacitors c 3 and c 4 connected to pins 1 and 9, and the charge time required for the ripple filter capacitor c 8 that is connected to pin 6. to ensure correct operation of this circuit, use the values given in the application example circuit for c 3 , c 4 , r 3 , r 4 , c 8 and r 8 . ! ! ! ! application board component layout (component side) (1) recording (2) playback fig.8 ba3308 ba3308 jpw jpw jpw r 8 r 6 r 2 r 5 r 1 r 4 r 3 r 7 c 7 c 6 c 4 c 2 c 1 c 3 c 8 c 5 r 8 c 6 c 8 c 5 r 4 r 12 r 10 r 11 r 9 r 3 c 4 c 3 c 2 c 10 c 9 c 1
ba3308 / BA3308F audio ics 7/8 ! ! ! ! electrical characteristic curves fig.9 quiescent current vs. power supply voltage 0 0246810121416 2 4 6 8 10 12 14 16 quiescent current : i q (ma) power supply voltage : v cc (v) fig.10 quiescent current vs. ambient temperature 0 ? 50 ? 25 0 25 50 75 100 2 4 6 8 10 12 quiescent current : i q (ma) ambient temperature : ta ( c) v cc = 7v fig.11 voltage gain vs. frequency 10 100 1k 10k 100k 40 0 10 20 30 50 60 70 80 90 100 g vo v cc = 7v v out = 300vrms r l = 10k ? frequency : f (hz) voltage gain : g v (db) flat nab fig.12 total harmonic distortion vs. frequency 10 100 1k 10k 100k 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 v cc = 7v v out = 1vrms r l = 10k ? nab frequency : f (hz) total harmonic distortion : thd (%) fig.13 voltage gain vs. power supply voltage 0 20 30 40 50 60 70 80 90 100 2 4 6 8 10 12 14 16 r 5 ,r 6 = 6.8k ? g vo voltage gain : g v (db) power supply voltage : v cc (v) r 5 ,r 6 = 39k ? v out = 300mvrms f = 1khz r l = 10k ? fig.14 closed loop voltage gain vs. ambient temperature 0 ? 50 ? 25 0 25 50 75 100 20 40 60 80 100 120 r 5 ,r 6 = 18k ? v cc = 7v v out = 300mvrms f = 1khz r l = 10kw closed loop voltage gain : g vo (db) ambient temperature : ta ( c) fig.15 input conversion noise voltage vs. signal source resistance 0.01 0.1 1 10 100 0.1 1 10 v cc = 7v g v = 52db r l = 10kw din audio input conversion noise voltage : v nin ( vrms) signal source resistance : rg (k ? ) fig.16 channel separation vs. frequency 10 100 1k 10k 100k ? 40 ? 100 ? 90 ? 80 ? 70 ? 60 ? 50 ? 30 ? 20 ? 10 0 v cc = 7v g v = 52db v out = 1vrms r l = 10k ? r g = 0 ? frequency : f (hz) channel separation : cs (db) fig.17 alc characteristics v cc = 7v f = 1khz g v = 52db v out ch2 ch1 ch1 ch2 thd ? 0 ? 80 ? 60 ? 40 ? 20 20 ? 40 ? 20 0 20 40 60 0 10 8 6 4 2 output voltage : v out (dbv) input voltage : v in (dbv) total harmonic distortion : thd (%)
ba3308 / BA3308F audio ics 8/8 fig.18 input/output characteristics ? 50 ? 40 ? 30 ? 20 v cc = 7v f = 1khz g v = 52db r l = 10k ? v out thd ? 60 ? 70 ? 80 1 10 0.1 0.01 output voltage : v out (vrms) total harmonic distortion : thd (%) input voltage : v in (dbv) fig.19 maximum output voltage vs. power supply voltage 0 0 2 4 6 8 10 12 14 16 1 1.2 1.4 1.6 f = 1khz thd = 1% r l = 10k ? 0.2 0.4 0.6 0.8 maximum output voltage : v om (vrms) power supply voltage : v cc (v) fig.20 maximum output voltage vs. load resistance 0 100 1k 10k v cc = 7v f = 1khz thd = 1% 2 1.8 1.6 1.4 1.2 1 0.2 0.4 0.6 0.8 maximum output voltage : v om (vrms) load resistance : r l ( ? ) ! ! ! ! external dimensions (units : mm) sip9 sop14 ba3308 BA3308F 2.54 10.5 0.5 3.5 0.5 1 1.2 5.8 0.2 0.6 9 0.3 0.1 0.8 1.3 21.8 0.2 2.8 0.2 0.4 0.1 1.27 1 14 8.7 0.2 7 8 4.4 0.2 6.2 0.3 0.11 1.5 0.1 0.15 0.15 0.1 0.3min.
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