ETC LS505

High Gain Class A Amplifier
with Peak Clipping
LS505 DATA SHEET
FEATURES
DESCRIPTION
• 72 dB typical gain
The LS505 is a low voltage, monolithic integrated circuit
amplifier comprised of an operational amplifier driving a
single transistor Class A output stage with open collector.
Also included are a pair of complementary Schottky diodes
which provide the capability for symmetrical peak clipping in
a feedback configuration.
• 0.2 to 2.0 mA of transducer current adjustment
• 43 dB range of feedback volume control
• 1.0 to 1.6 V supply operating range
• Schottky diodes provide symmetrical peak clipping
An internal negative feedback loop ensures a stable operating
point for the output stage over the designed operating voltage.
This also permits trimming of the output current with the use
of a single external resistor.
• requires only 4 external parts for operation
STANDARD PACKAGING
• 8 pin MINIpac
The input stage and microphone are biased by an internal
2.2 kΩ decoupling resistor to increase battery line signal
rejection.
• 8 pin MICROpac
• 8 pin PLID®
• 8 pin SLT
• Chip (56 x 55 mils)
VMIC
8
VB
MPO
4
1
O/P
2.2k
I/P
3
+
6
33k
100
RVC
200
5
7
GND
2
RE
BLOCK DIAGRAM
All resistors in ohms, all capacitors in farads unless otherwise stated.
Revision Date: January 1996
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
Document No. 500 - 20 - 11
tel. (905) 632-2996 fax: (905) 632-5946
tel. (03) 3334-7700
fax (03) 3247-8839
PIN CONNECTION
ABSOLUTE MAXIMUM RATINGS
PARAMETER
VALUE & UNITS
Supply Voltage
V
B
3V
Power dissipation
-10 to +40 °C
Storage Temperature
-20 to +70 °C
R
VC
O/P
25 mW
Operating Temperature
5
4
I/P
R
E
GND
MPO
V
MIC
1
8
CAUTION
CLASS 1 ESD SENSITIVITY
ELECTRICAL CHARACTERISTICS
Conditions: Temperature 25 o C, Supply Voltage VB = 1.55 VDC
PARAMETER
SYMBOL
CONDITION
MIN
TYP
MAX
VO = 0.707 VRMS
68
72
76
-
0.07
-
180
210
280
-
-0.002
-
1.3
1.5
1.9
UNITS
Gain
ACL
Temperature Coefficient of Gain
ηA
Amplifier Current
IAMP
Temperature Coefficient of Current
ηΙ
Transducer Current
ITRANS
Total Harmonic Distortion
THD
VO = 0.707 VRMS
-
2
5
Input Referred Noise
IRN
NFB 0.2 to 10 kHz at 12 dB/oct
-
1.2
2.0
µVRMS
Battery Resistance Stability
RB = 22Ω
-
-
22
Ω
Volume Control Range
RVC = 100 to 100.1 kΩ S1 open
36
43
-
dB
-
27
-
kΩ
Low
-
100
-
Hz
High
-
5K
-
Hz
0.125
0.19
0.275
VRMS
-
0.16
-
dB/Ω
-
42.5
-
mV
Input Impedance (Pin 6)
RIN
Frequency Response (-3 dB)
Maximum Output
S2 closed
Gain Dependence of RB
Emitter Bias Voltage (Pin 2)
VRE
All switches and parameters remain as shown in test circuit unless stated in condition column
500 - 20 - 11
2
dB
dB/oC
µA
mA/oC
mA
%
RB = 4.7
10
+
+
VB = 1.5 VDC
VO
10
S2
1k
8
RS
3.9k
2.2k
1
4
3
0.033
IL
+
6
S1
33k
200
100
100k
+
10
100
5
2
7
RE
33
All resistors in ohms, all capacitors in µF unless otherwise stated
Fig. 1 Test Circuit
VB
4
2.2k
MPO
VMIC
1
8
30k
27k
OUTPUT
3
INPUT
6
100
33k
VOLUME
CONTROL
2
RE
200
5
GND
7
All resistors in ohms, all capacitors in farads unless otherwise stated
U.S. Patent No. 4,034,306 - Patented in other countries
Fig. 2 Functional Schematic
3
500 - 20 - 11
CMPO
+
V =1.35VDC
B
RMPO
10
10k
1.0
8
4
1
1k
2.2k
3
6
+
0.033
LS505
100
-
5
RVC
33k
200
100k
LS505
2
7
+
10
R
E
56
All resistors in ohms, all capacitors in farads unless otherwise stated
7
46
6
45
5
44
4
)
47
Ω
gm (
43
3
42
2
41
1
40
10
50
100
500
1k
5k
0
10k
10
50
100
500
Fig. 5 GM
Fig. 4 Volume Control Range vs RE
3.5
5k
10k
100
110
vs RE Ω
130
DIODES
DISCONNECTED
3.0
120
OUTPUT (dBSPL)
2.5
L
LOAD CURRENT I (mA)
1k
RE Ω
EXTERNAL RESISTANCE (Ω)
Ω
VOLUME CONTROL RANGE (dB)
Fig. 3 Typical Hearing Aid Applications
2.0
1.5
1.0
110
100
90
0.5
0
10
80
50
100
500
1k
5kk
10k
40
50
60
70
80
Fig. 7 I/O Characteristics
Fig. 6 Load Current vs External Resistance
500 - 20 - 11
30
INPUT (dBSPL)
EXTERNAL RESISTANCE RE (Ω)
4
90
6
RELATIVE VOLTAGE GAIN (dB)
RELATIVE VOLTAGE GAIN (dB)
0
-10
-20
-30
-40
-50
10
100
1k
R
VC
5
4
3
2
1
10k
1
100
BATTERY RESISTANCE R (Ω)
B
Fig. 8 Relative Voltage Gain vs
Volume Control Resistance
Fig. 9 Relative Voltage Gain vs
Battery Resistance
250
2.5
200
2.0
L
LOAD CURRENT I (mA)
AMPLIFIER CURRENT (µA)
10
(Ω)
150
100
50
0
1.5
1.0
0.5
0
0.8
1.0
1.2
1.4
1.6
0.8
1.8
1.0
1.2
1.4
1.6
1.8
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Fig. 10 Amplifier Current vs Supply Voltage
Fig. 11 Load Current vs Supply Voltage
74
GAIN (dB)
72
70
68
66
64
0.8
1.0
1.2
1.4
1.6
1.8
SUPPLY VOLTAGE (V)
Fig. 12 Gain vs Supply Voltage
REVISION NOTES
Au bump removed
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 1977 Gennum Corporation. All rights reserved. Printed in Canada.
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