GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-5946
Japan Branch: A-302, M i yamae Vi l l age, 21042 M i yamae, Suginamiku, Tokyo 168, Japan tel. (03) 3334-7700 fax (03) 3247-8991
Class A Amplifier with
3 Independent Gain Blocks
GC509 DATA SHEET
Document No. 510 - 70 - 3
DESCRIPTION
The GC509 is a Class A amplifier utilizing Gennum's proprietary
low voltage JFET technology. It consists of two single-
ended, 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 (R
E
). To increase the bias current in the transducer,
simply place an external R
E
resistor from pin 8 to ground,
thereby decreasing the equivalent emitter resistance and
increasing the current.
BLOCK DIAGRAM
All resistors in ohms, all capacitors in Farads unless otherwise
stated
C OUT
B IN
R
B OUT
V
E
B
GND
A OUT
A IN
V
MIC
C IN
1
4
2
10
9
21K
5
R
MIC
3
8
- A
- B
7
6
- C
R
E
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
STANDARD PACKAGING
10 pin MICROpac
10 pin PLID
10 pin SLT
Chip (61 x 55 mils)
Au Bump
2
510 - 70 - 3
R
L
= 1K
RB = 4.7
1
4
2
10
9
21K
R
FA =
56.2K
5
R
MIC
1kHz
3
2.7K
8
- A
C
S
1.0
1.0
- B
R
FB =
47.5K
7
6
R
E =
47.5
VOUT
1.3 VDC
0.015
1.0
R
S
3.3K
V
IN
S1
a
b
- C
R
E
Fig.1 Test Circuit
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
5
10
1
6
CAUTION
CLASS 1 ESD SENSITIVITY
C OUT
R
E
B OUT
C IN
V
B
GND
B IN
A IN
V
MIC
A OUT
PIN CONNECTION
All resistors in ohms, all capacitors in Farads unless otherwise stated
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Amplifier Current
I
AMP
80
145
210
A
Transducer Current
I
TRANS
R
E
=
200
275
350
A
Maximum Transducer Current
I
TRANS(MAX)
R
E
= 0
2
- - mA
Input Bias Current
I
BIAS
R
FA
= 1M, R
FB
= 1M
-50
0
50
nA
Input Referred Noise
IRN
NFB 0.2 to 10kHz at 12dB/Oct
-
1
2
V
RMS
Harmonic Distortion
THD
S1 = b, V
OUT
= 500 mV
RMS
-
1
4
%
Voltage Gain
A
V
S1 = b, V
OUT
= 500 mV
RMS
70
73
76
dB
Stable with Battery Resistance
Stability
R
B
= 22
-
-
22
Resistance (R
B
) to:
Emitter Bias Voltage (Pin 8)
V
RE
-
55
-
mV
Microphone Resistance
R
MIC
3
4
5
k
On Chip Emitter Resistor
R
E
-
200
-
Preamp Current Drive Capability
I
OUT
-
30
-
A
All switches remain as shown in Test Circuit unless otherwise stated in CONDITIONScolumn.
ELECTRICAL CHARACTERISTICS
Conditions: Frequency = 1 kHz, Temperature = 25
o
C, Supply Voltage = 1.3 VDC
3
510 - 70 - 3
R
MIC
5
2
4
3
10
9
33K
6
7
8
1
R
E
BASE CURRENT
COMPENSATION
21K
Fig. 3 Typical Hearing Aid Circuit
R
VC
Gain of stage B = 20 Log
5.6K
R
GT
Gain of stage A = 20 Log
R
S
R
LAC//21K
Gain of stage C = 20 Log
R
E/120
10
10
10
Fig. 2 Functional Schematic
All resistors in ohms, all capacitors in Farads unless otherwise stated.
ED1913
R
LAC
VB = 1.3 VDC
4
21K
5
R
MIC
R
S
= 3.9K
8
- A
C
S
0.22
1.0
120
- B
- C
7
6
1
2
10
9
R
GT
3
5.6K
100K
100K
0.1
R
VC
R
E
4
510 - 70 - 3
0
-10
-20
-30
-40
-50
-60
-70
-80
10
0
-10
-20
-30
-40
-50
-60
-70
-20 -10 0 10 20 30 40 50
TEMPERATURE (
o
C)
10
5
0
-5
-10
-15
-20
RELATIVE TRANSDUCER CURRENT
(
A)
-20 -10 0 10 20 30 40 50
TEMPERATURE (
o
C)
RELATIVE AMPLIFIER CURRENT (
A)
30
20
10
0
-10
-20
-30
-40
0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
SUPPLY VOLTAGE (V)
RELATIVE GAIN (dB)
20 200 2k 20k
FREQUENCY (Hz)
C
S
= 0.22
C
S
= 0.047
C
S
= 0.1
C
S
= 0.033
RELATIVE OUTPUT (dB)
Fig. 5. Closed Loop Frequency Response
with Various C
S
Values
4
0
-4
-8
-12
-16
-20
OUTPUT (dBV)
GAIN (dB)
60
55
50
45
40
35
30
25
20
10 100 1K 10K 100K
FREQUENCY (Hz)
Fig. 7 Preamplifier Open Loop Frequency Response
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.
Copyright July 1989 Gennum Corporation. Revision Date: July 1992
All rights reserved.
Printed in Canada.
Fig. 4 I/O Curves at Various R
VC
Settings
-140 -120 -100 -80 -60
-40
INPUT (dBV)
R
VC
= 100K
R
VC
= 47K
R
VC
= 22K
R
VC
= 10K
R
VC
= 3.3K
Fig. 8 Transducer Current vs Temperature
Fig. 9 Amplifier Current vs Temperature
Fig. 6 Gain vs Supply Voltage
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.
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