Class A Amplifier with
3 Gain Blocks & Schottky Diodes
LS509 DATA SHEET
FEATURES
• 140
µA
typical current drain
•
low noise and distortion
DESCRIPTION
The LS509 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, an on-chip microphone decoupling resistor and a
pair of Schottky diodes for symmetrical peak clipping.
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 LS509 is a Class A current drive.
It has a fixed reference voltage of typically 29 mV at pin 2
of the device. The current that flows in the transducer is the
ratio of the 29 mV reference voltage and the on-chip
emitter resistor (R ). To increase the bias current in the
E
transducer, simply place an external RE resistor from pin
2 to ground, thereby decreasing the equivalent emitter
resistance and increasing the current.
The LS509 also contains a pair of Schottky diodes in the
feedback configuration of the output stage, which provides
approximately 12 dB of MPO control.
V
B
8
V
MIC
• 1.0 to 5 VDC operating range
•
•
•
•
•
•
independent preamplifier
2 DC coupled stages
class A output stage
variable transducer current
Schottky diodes for MPO control
4 kΩ microphone decoupling resistor
STANDARD PACKAGING
• 10 pin PLID
• 10 pin SLT
• Chip (61 x 55 mils)
®
7
R
MIC
9
MPO
21k
A I/P
6
-
A
-
B
-
C
10
2
R
E
C O/P
R
E
5
A O/P
4
B I/P
3
B O/P
1
GND
All resistors in ohms, all capacitors in farads unless otherwise stated
BLOCK DIAGRAM
Revision Date: January 2001
Document No. 510 - 12 - 08
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
-10°C to 40° C
-20°C to 70° C
A OUT
B IN
B OUT
R
E
GND
PIN CONNECTION
5
6
A IN
V
MIC
V
B
MPO
1
10
C OUT
CAUTION
CLASS 1 ESD SENSITIVITY
ELECTRICAL CHARACTERISTICS
V
P
- Pin voltage measured with conditions as shown in Test Circuit.
Positive current corresponds to current INTO the pin.
Negative current corresponds with current OUT of the pin.
Conditions: Frequency = 1 kHz, Temperature = 25°C, Supply Voltage V
B
= 1.3 V
PARAMETER
Amplifier Current
Transducer Current
Maximum Transducer Current
A Input Bias Voltage (pin 6)
A Input Bias Current (pin 6)
B Input Bias Current (pin 4)
A O/P Voltage Swing-Hi (pin 5)
A Output Swing-Lo (pin 5)
SYMBOL
I
AMP
I
TRANS
I
TRANS (MAX)
V
BIAS A
I
BIAS A
I
BIAS B
V
OH A
V
OL A
A
OL
V
SAT C
A
OUT
V
D
V
RE
R
MIC
R
E
IRN
THD
CONDITIONS
MIN
75
170
TYP
140
230
-
570
0
0
580
280
MAX
205
290
-
650
50
50
-
-
UNITS
µA
µA
mA
mV
nA
nA
mV
mV
V
P2
= 0 V
R
FA
= 1 M (Note 1)
V
IN
= 0.4 V DC, R
FA
=
∞
,
I
P5
= -10
µA
(Note 3)
I
IN
= +1µA, R
FA
=
∞
,
I
P5
= +10
µA
(Note 4)
R
L
= 1 kΩ, V
P2
= 0 V
(S2 = b) R
L
=
R
FB
= 1 M (Note 2)
2
500
-50
-50
200
200
A Open Loop Voltage Gain
C Output Sat. Voltage (pin 10)
A Output Current Capability (pin 5)
46
-
-
56
100
30
265
28.5
4
125
1
1
-
180
-
325
35.5
5
160
-
-
dB
mV
µA
mV
mV
kΩ
Ω
µVRMS
%
Diode Voltage Drop
Emitter Bias Voltage (pin 2)
On-chip Microphone Resistor
On-chip Emitter Resistor
Input Referred Noise
Harmonic Distortion
∞
,
(Note 5)
140
21.5
3
90
NFB 0.2 to10kHz at 12dB/Oct
V
OUT
= 500 mV
RMS
-
-
All parameters and switches remain as shown in Test Circuit unless otherwise stated in "Conditions" column
Notes
1.
I
BIAS A
= (V
P6
-V
P6[RFA = 1M]
)/1M
2.
I
BIAS B
= (V
P4
-V
P4 [RFB = 1M]
)/1M
3.
V
OH A
= (V
P5
-V
P5 [VIN = 0.4 VDC, RFA =
∞,
IP5
= -10µA]
)
4.
V
OL A
= (V
P5
-V
P5 [IIN = +1µA, RFA =
∞,
IP5
=+10µA]
)
V
)
5.
V
D
= (V
P10
[Id = +(1.5 x
ITRANS)]
- P10 [Id = +(0.5 x
ITRANS)]
510 - 12 - 08
2
I
AMP
1.3 VDC
I
TRANS
8
7
R
MIC
9
a
V
IN
a
R
S
3k92
C
S
1µ0
R
E
5
180 µV
RMS
1kHz
R
FA
= 0
4
R
FB
= 0
3
1
b
S1
6
21k
S2
b
R
L
=0
-
A
-
B
-
C
10
2
I
d
= 0µA
I
P5
= 0µA
All resistors in ohms, all capacitors in farads unless otherwise stated.
Fig. 1 Test Circuit
R
MIC
7
8
9
5
BASE
CURRENT
COMPENSATION
3
R
E
10
2
6
4
1
All resistors in ohms, all capacitors in farads unless otherwise stated.
Fig. 2 Functional Schematic
3
510 - 12 - 08
V
B
= 1.3 V DC
ED1913
8
7
1µ0
R
MIC
21k
9
0µ1
R
MPO
R
S
≈
3k9
C
S
0µ22
6
50k
RL
AC
-
A
- B
-C
10
2
R
E
0µ1
5
100k
R
GT
0µ1 5k6
4
100k
3
1
56
R
VC
All resistors in ohms, all capacitors in farads unless otherwise stated.
Gain of Stage A = 20 log
R
GT
R
S
Gain of Stage B = 20 log
R
VC
5.6 k
Gain of Stage C = 20 log
RL
AC
//21K
56//R
E
Fig 3 Typical Hearing Instrument Application
5
-5
-15
0
-2
R
MPO
= 50k
R
MPO
= 22k
R
MPO
= 10k
R
VC
= 100K
-4
-6
OUTPUT (dBV)
-25
-35
-45
-55
-65
-75
-140
R
VC
= 47K
R
VC
= 10K
R
VC
= 3.3K
OUTPUT (dBV)
-8
-10
-12
-14
-16
R
MPO
= 0k
R
MPO
= 3.3k
R
VC
= 22K
-120
-100
-80
-60
-40
-18
-20
-90
-80
-70
-60
-50
-40
INPUT (dBV)
INPUT (dBV)
Fig. 4 I/O Curves at Various R
VC
Settings
4
5
Fig. 5 I/O Curves at Various R
MPO
Values
C
S
= 0.22µ
0
0
C
S
= 0.1µ
RELATIVE GAIN (dB)
-4
RELATIVE GAIN (dB)
C
S
= 0.033µ
-5
-10
-15
-20
-25
-30
-8
C
S
= 0.047µ
-12
-16
-20
20
200
2k
20k
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
Fig. 6 Closed Loop Frequency Response
with Various C
S
Values
510 - 12 - 08
Fig. 7 Gain vs Supply Voltage
4
RELATIVE TRANSDUCER CURRENT (µA)
-10
0
10
20
30
40
50
0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-20
10
6
2
-2
-6
-10
-14
-18
-20
-10
0
10
20
30
40
50
RELATIVE GAIN (dB)
TEMPERATURE (
o
C)
TEMPERATURE (
o
C)
Fig. 8 Gain vs Temperature
Fig. 9 Transducer Current vs Temperature
24
60
55
50
RELATIVE AMPLIFIER CURRENT (µA)
16
8
-8
-16
-24
-32
-40
-20
Gain (dB)
0
45
40
35
30
25
20
-10
0
10
20
30
40
50
10
100
1k
10k
100k
TEMPERATURE (
o
C)
FREQUENCY (Hz)
Fig. 10 Amplifier Current vs Temperature
Fig. 11 Preamplifier A Open Loop Frequency Response
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.
© Copyright October 1987 Gennum Corporation.
All rights reserved.
Printed in Canada.
5
510 - 12 - 08
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