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Class A Amplifier with 3 Independent Gain Blocks
GC509 DATA SHEET
FEATURES * 145 A typical current drain * low noise and distortion * 1.0 to 5 VDC operating range * 2 independent preamplifiers * Class A output stage * variable transducer current * 4 k microphone decoupling resistor
DESCRIPTION The GC509 is a Class A amplifier utilizing Gennum's proprietary low voltage JFET technology. It consists of two singleended, low noise inverting gain blocks, a Class A output stage, and an on-chip microphone decoupling resistor. Blocks A and B typically have 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 GC509 is a Class A current drive. It has a fixed reference voltage of typically 55 mV at pin 8 of the device. The current that flows in the transducer is the ratio of the 55 mV reference voltage and the on-chip emitter resistor (RE ). To increase the bias current in the transducer, simply place an external RE resistor from pin 8 to ground, thereby decreasing the equivalent emitter resistance and increasing the current.
STANDARD PACKAGING * 10 pin MICROpac * 10 pin PLID (R) * 10 pin SLT * Chip (61 x 55 mils) Au Bump
VB VMIC 5 RMIC 6
21K 4 A IN
-A
-B
-C
7 8 RE
C OUT RE
2
3
10 B OUT
9 C IN
1 GND
A OUT B IN
All resistors in ohms, all capacitors in Farads unless otherwise stated
BLOCK DIAGRAM
Document No. 510 - 70 - 3
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3
Japan Branch: A-302, M i yamae Vi l l age, 2-10-42 M i yamae, Suginami-ku, Tokyo 168, Japan
tel. (905) 632-2996 fax: (905) 632-5946
tel. (03) 3334-7700 fax (03) 3247-8991
ABSOLUTE MAXIMUM RATINGS
PARAMETER Supply Voltage Power Dissipation Operating Temperature Storage Temperature VALUE / UNITS 5V DC 25 mW -10o to + 40oC -20o to + 70oC VMIC
A IN B IN A OUT GND
PIN CONNECTION
5
6
VB C OUT RE C IN
1
10
B OUT
CAUTION CLASS 1 ESD SENSITIVITY
ELECTRICAL CHARACTERISTICS
Conditions: Frequency = 1 kHz, Temperature = 25o C, Supply Voltage = 1.3 VDC
PARAMETER Amplifier Current Transducer Current Maximum Transducer Current Input Bias Current Input Referred Noise Harmonic Distortion Voltage Gain Stable with Battery Resistance Resistance (RB) to: Emitter Bias Voltage (Pin 8) Microphone Resistance On Chip Emitter Resistor Preamp Current Drive Capability
SYMBOL I AMP I TRANS I TRANS(MAX) I BIAS IRN THD AV Stability VRE R MIC RE I OUT
CONDITIONS
MIN 80
TYP 145 275 0 1 1
73
MAX 210 350 50 2 4
76
UNITS A A mA nA VRMS %
dB
RE= RE= 0 RFA = 1M, RFB = 1M NFB 0.2 to 10kHz at 12dB/Oct S1 = b, VOUT = 500 mVRMS S1 = b, VOUT = 500 mVRMS RB = 22
200 2 -50 70
3 -
55 4 200 30
RB = 4.7
22 5 -
mV k A
All switches remain as shown in Test Circuit unless otherwise stated in CONDITIONScolumn.
1.3 VDC 5 RMIC 6 VOUT 21K 4 S1 RL = 1K
RS
VIN a CS
-A
-B
-C
3.3K 1.0 b
7 8 RE
2 1kHz RFA = 56.2K 2.7K
3
10
9
1 0.015 RE = 47.5
RFB = 47.5K 1.0
1.0
All resistors in ohms, all capacitors in Farads unless otherwise stated
Fig.1 Test Circuit
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510 - 70 - 3
5
RMIC 21K
6 7
BASE CURRENT COMPENSATION
2
10
9 33K 8
3 4 RE 1
Fig. 2 Functional Schematic
VB = 1.3 VDC
RMIC 1.0 5
6 ED1913 RLAC
21K
-A
RS = 3.9K CS 0.22 4
-B
-C
7 8
RE 2 100K 5.6K 3 100K 0.1 RVC 10 9 1
120
RGT
All resistors in ohms, all capacitors in Farads unless otherwise stated.
Gain of stage A = 20 Log 10
RGT RS
Gain of stage B = 20 Log 10
RVC 5.6K
Gain of stage C = 20 Log
RLAC//21K 10 RE/120
Fig. 3 Typical Hearing Aid Circuit
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510 - 70 - 3
0 -10 -20
RVC = 100K RVC = 47K R = 22K RVC = 10K
4
CS = 0.22
0
RELATIVE OUTPUT (dB)
CS = 0.1
-4
OUTPUT (dBV)
-30 -40 -50 -60 -70 -80 -140
VC
-8
CS = 0.047
-12
RVC = 3.3K
-16
CS = 0.033
-20 -120 -100 -80 -60 -40 20 200 2k 20k
INPUT (dBV)
FREQUENCY (Hz)
Fig. 4 I/O Curves at Various RVC Settings
Fig. 5. Closed Loop Frequency Response with Various CS Values
10 0
60 55 50
RELATIVE GAIN (dB)
-10
-30 -40 -50 -60 -70
GAIN (dB)
0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
-20
45 40 35 30 25 20 10
100
1K
10K
100K
SUPPLY VOLTAGE (V)
FREQUENCY (Hz)
Fig. 6 Gain vs Supply Voltage
10 30
Fig. 7 Preamplifier Open Loop Frequency Response
RELATIVE TRANSDUCER CURRENT (A)
RELATIVE AMPLIFIER CURRENT (A)
5
20 10 0 -10 -20 -30 -40
0
-5
-10
-15
-20
-20
-10
0
10
20
30
40
50
-20
-10
0
10
20
30
40
50
TEMPERATURE ( oC)
TEMPERATURE (o C)
Fig. 8 Transducer Current vs Temperature
Fig. 9 Amplifier Current vs Temperature
DOCUMENT IDENTIFICATION
PRODUCT PROPOSAL This data has been compiled for market investigation purposes only, and does not constitute an offer for sale.
REVISION NOTES
Changes to standard packaging. 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 July 1989 Gennum Corporation. All rights reserved. Printed in Canada. Revision Date: July 1992
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.
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510 - 70 - 3

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