gennum corporation p.o. box 489, stn a, burlington, ontario, canada l7r 3y3 tel. (905) 632-2996 fax: (905) 632-2055 japan branch: a-302, m i yamae villa ge, 2C10C42 m i yamae, suginami Cku, tokyo 168, japan tel. (03) 3247-8838 fax (03) 3247-8839
class a amplifier with 2 independent gain blocks GP509 data sheet document no. 510 - 71 - 04 features ? low amplifier current (typical 105 m a) ? low noise and distortion ? 1.0 to 5 vdc operating range ? independent preamplifier ? class a output stage ? variable transducer current ? 4.0 k w microphone decoupling resistor, on-chip description the GP509 is a class a amplifier utilizing gennums proprietary low voltage jfet technology. it consists of a single- ended, low noise inverting gain block, a class a output stage, and an on-chip microphone decoupling resistor. block a typically has an open loop voltage gain of 56 db, with the closed loop gain set by the ratio of the feedback resistor to the source impedance. it is recommended that the maximum closed loop gain be 20 db lower than the open loop gain. all blocks of the device are internally bias compensated, preventing any dc current flow via external feedback resistors. without this compensation, audible scratchiness would be present during changes in volume control settings. the output stage of the GP509 is a class a current drive. it has a fixed reference voltage of typically 30 mv at pin 7 of the device. the current that flows in the transducer is the ratio of the 30 mv reference voltage and the on-chip emitter resistor (r e ). to increase the bias current in the transducer, simply place an external r e resistor from pin 7 to ground, thereby decreasing the equivalent emitter resistance and increasing the current. standard packaging ? 8 pin micropac ? 8 pin plid ? ? 8 pin slt ? chip (61 x 55 mils) block diagram - a - b b in r b out v e b gnd a out a in v mic 1 2 4 3
r mic 8 7 5 r e
21k 6 revision date: january 1996
2 510 - 71 - 04 1.3 vdc r =27.5 e 1.0 5 7 8 2 - b - a r e 21k 6 r l = 1k r mic 4 3 1 r =100k fa 1 khz r s r b = 4.7 v in s1 a b 3k3 1.0 c s v out 1 4 5 8 v mic gnd a in a out b in r e b out v b pin connection absolute maximum ratings parameter value / units supply voltage 5v dc power dissipation 25 mw operating temperature -10 o to + 40 o c storage temperature -20 o to + 70 o c caution class 1 esd sensitivity parameter symbol conditions min typ max units amplifier current i amp 55 105 150 m a transducer current i trans r e = 225 300 375 m a maximum transducer current i trans(max) r e = 0 w 2 - - ma voltage gain a v s1 = b v out = 500 mv rms 58 61 64 db harmonic distortion thd s1 = b v out = 500 mv rms - 1 4 % input referred noise irn nfb 0.2 to 10 khz at 12db/oct - 1 2 m v rms stable with battery resistance resistance (r b ) to: stability r b = 22 w - - 22 w input bias current i bias r fa = 1m -50 0 50 na microphone resistance r mic 3 4 5 k w emitter bias voltage (pin 7) v re - 30 - mv on chip emitter resistor r e - 100 - w a output current capability (pin 1) i out - 30 - m a note: all parameters and switches as shown in test circuit unless otherwise stated in conditions column electrical characteristics supply voltage = +1.3 vdc, frequency = 1 khz, temperature = 25 o c all external resistors in ohms & 1% tol., all capacitors in farads & 10% tol. unless otherwise stated fig. 1 test circuit
3 510 - 71 - 04 - a - b b in r b out v e b gnd a out a in v mic 1 2 4 3
r mic 8 7 5 r e
21k 6 10 r s 10 a = 20 log r vc b = 20 log r lac // 21k gain of stage gain of stage fig. 3 typical hearing aid circuit r e // 82 all resistors in ohms, all capacitors in farads unless otherwise stated. fig. 2 functional schematic r mic 6 ed1913
r lac 2 v =1.3vdc 1 4 3 5 r e 82 21k 7 - a 1.0 b c s
0.22 - b 100k r vc
r s 3k9
8
4 510 - 71 - 04 fig. 8 transducer current vs temperature fig. 9 amplifier current vs temperature -20 -10 0 10 20 30 40 50 temperature ( o c) 15 10 5 0 -5 -10 -15 -20 -25 relative transducer current ( m a) 20 15 10 5 0 -5 -10 -15 -20 -25 -30 relative amplifier current ( m a) -20 -10 0 10 20 30 40 50 temperature ( o c) 10 100 1k 10k 100k frequency (hz) fig.7 preamplifier open loop frequency response document identification product proposal this data has been compiled for market investigation purposes only, and does not constitute an offer for sale. advance information note this product is in development phase and specifications are subject to change without notice. gennum reserves the right to remove the product at any time. listing the product does not constitute an offer for sale. preliminary data sheet the product is in a development phase and specifications are subject to change without notice. data sheet the product is in production. gennum reserves the right to make changes at any time to improve reliability, function or design, in order to provide the best product possible. gennum corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. ? copyright 1989 gennum corporation. all rights reserved. printed in canada. revision notes au bump removed 20 200 2k 20k frequency (hz) c s = 0.22 m c s = 0.1 m c s = 0.047 m c s = 0.033 m 4 2 0 -2 -4 -6 -8 -10 -12 -14 -16 -18 -20 output (dbv) fig. 5 closed loop frequency response for various c s values 60 55 50 45 40 35 30 25 20 gain (db) 10 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 output (dbv) input (dbv) r vc = 100k r vc = 47k r vc = 22k r vc = 10k -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 fig.4 i/o characteristics for various gain settings fig.6 gain vs supply voltage 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 supply voltage (v) 5 0 -5 -10 -15 -20 -25 -30 -35 relative gain (db) r vc = 3.3k
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