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Class A Amplifier with 2 Independent Gain Blocks LP508 DATA SHEET FEATURES * 1 V input referred noise * 1.0 to 5 VDC operating range * 61 dB typical gain (adjustable) * 0.28 to 2.0 mA range of transducer current * 1 % electrical distortion * the first and second blocks can be DC coupled * 4.0 k microphone decoupling resistor, on-chip * 100 Hz to 50 kHz frequency response * volume control range >40 dB STANDARD PACKAGING * * * * 8 pin MICROpac 8 pin PLID (R) 8 pin SLT Chip (59 x 53 mils) Au Bump DESCRIPTION The LP508 is an 8 pin Class A amplifier utilizing Gennum's proprietary low voltage bipolar JFET technology. It consists of 2 single ended, low noise inverting gain blocks. The first block has a typical open loop gain of 50 dB, with the closed loop gain set by the ratio of the feedback resistor to the the source impedance. The second block has the output transistor bias set by RE and VRE at pin 7 which is 27 mV. Typically, the gain of the first block is set to 29 dB, with the second block at 32 dB, giving a total gain of 61 dB. VB 5 VMIC 4 RMIC 18K 3 A IN 6 -A -B 7 RE 1 A OUT 8 B IN 2 GND B OUT RE BLOCK DIAGRAM Revision Date: January 2001 Document No. 500 - 71 - 9 GENNUM CORPORATION P.O. Box 489, Stn. A, Burlington, Ontario, Canada L7R 3Y3 tel. +1 (905) 632-2996 Web Site: www.gennum.com E-mail: hipinfo@gennum.com ABSOLUTE MAXIMUM RATINGS PARAMETER Supply Voltage Power Dissipation Operating Temperature Range Storage Temperature Range VALUE/UNITS 5 V DC 25 mW -10C to 40 C -20C to 70 C V MIC A IN GND A OUT PIN CONNECTION 4 5 V B B OUT R E 1 8 B IN CAUTION CLASS 1 ESD SENSITIVITY ELECTRICAL CHARACTERISTICS Conditions: Frequency = 1 kHz, Temperature = 25C, Supply Voltage VB = 1.3 VDC PARAMETER Gain (Closed Loop) Distortion Amplifier Current Transducer Current Transducer Current Input Referred Noise Stable with Battery Resistance to Input Bias Current (pin 3) On Chip Emitter Resistor Emitter Bias Voltage (Pin 7) Microphone Decoupling Resistor SYMBOL A CL THD IAMP ITRANS H ITRANS L IRN CONDITIONS VOUT=500mVRMS VOUT=500mVRMS IAMP= I A + I MIC RE = 27.5 RE = NFB 0.2 to 10 kHz at 12 dB/oct. MIN 57 125 1.1 200 - TYP 61 1 195 1.3 275 1 0 100 27 4 MAX 65 4 255 1.7 350 2 22 50 - UNITS dB % A mA A V nA mV k IB RE VRE R MIC -50 - All parameters and switches remain as shown in Test Circuit unless otherwise stated in "Conditions" column IAMP VB=1.3 VDC RB= 4.75 IMIC 4 RS 3.3K 33K V IN 1kHz C2 10 C1 10 3 RMIC 5 VOUT RL=1K 6 18K -A -B 7 ITRANS IB RE RE =27.5 1 RFA =100K C3 1.0 8 2 All resistors in ohms, all capacitors in F unless otherwise stated Fig. 1 Test Circuit 500 - 71 - 9 2 5 RMIC 18K 6 1 BASE CURRENT COMPENSATION 33K 8 7 3 RE Patent No.154104 All resistors in ohms, all capacitors in F unless otherwise stated 2 Fig. 2 Functional Schematic VB = 1.3 VDC 5 RMIC 1.0 CS 4 RL = 6K 18K 6 -A RS 3.9K 0.22 3 -B 7 RE 1 8 2 RVC 100K Gain of stage A = 20Log10 RVC RS Gain of stage B = 20 10 RL // 18K Log RE For low impedance receivers, a capacitor from pin 6 to pin 2 may be required for stability. All resistors in ohms, all capacitors in F unless otherwise stated Fig. 3 Typical Hearing Aid Circuit 3 500 - 71 - 9 10 0 -10 -20 RVC = 100K RVC = 47K RVC = 22K RVC = 10K RVC = 3.3K -50 -60 -70 -80 -90 -130 -110 -90 -70 -60 -40 -20 4 2 0 CS = 0.22F RELATIVE OUTPUT (dB) -2 -4 -6 -8 -10 -12 -14 -16 -18 -20 20 CS = 0.1F OUTPUT (dBV) -30 -40 CS = 0.047F CS = 0.033F 20000 INPUT (dBV) FREQUENCY (Hz) Fig. 4 I/O Characteristics at Various RVC Values 10 5 0 60 55 50 Fig. 5 Frequency Response at Various CS Values RELATIVE GAIN (dB) -5 -15 -20 -25 -30 -35 -40 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 GAIN (dB) -10 45 40 35 30 25 20 10 100 1K 10K 100K SUPPLY VOLTAGE (VDC) FREQUENCY (Hz) Fig. 6 Gain vs Supply Voltage 40 30 20 10 0 -10 -20 -30 -40 -50 -60 -20 -10 0 10 20 30 40 50 30 20 10 0 -10 -20 -30 -40 -50 -20 Fig. 7 Preamplifier A Open Loop Frequency Response RELATIVE TRANSDUCER CURRENT (A) RELATIVE AMPLIFIER CURRENT (A) -10 0 10 20 30 40 50 TEMPERATURE (C) TEMPERATURE (C) Fig. 8 Amplifier Current vs Temperature Fig. 9 Transducer Current vs Temperature GENNUM CORPORATION MAILING ADDRESS: P.O. Box 489, Stn. A, Burlington, Ontario, Canada L7R 3Y3 Tel. +1 (905) 632-2996 Fax +1 (905) 632-2814 SHIPPING ADDRESS: 970 Fraser Drive, Burlington, Ontario, Canada L7L 5P5 DOCUMENT IDENTIFICATION: 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. REVISION NOTES: Changes to standard packaging information GENNUM JAPAN CORPORATION C-101, Miyamae Village, 2-10-42 Miyamae, Suginami-ku, Tokyo 168-0081, Japan Tel. +81 (3) 3334-7700 Fax: +81 (3) 3247-8839 Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. (c) Copyright May 1984 Gennum Corporation. All rights reserved. Printed in Canada. 500 - 71 - 9 4 |
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