Low Current, Peak Limiting
Class A Amplifier
LT505 DATA SHEET
FEATURES
• amplifier current typically 53
µ
A
• transducer current typically 210
µ
A
• Schottky diodes provide peak limiting
• low parts count
• gain 74dB typically with 1.3 V supply
STANDARD PACKAGING
• 8 Pin MICROPAC
• 8 Pin MINIPAC
• 8 Pin PLID
®
• 8 Pin SLT
• chip ( 56 x 55 mils)
Au Bump
DESCRIPTION
The LT505 is a low current, low voltage monolithic integrated
circuit amplifier. It is comprised of an operational amplifier
driving a single transistor class A output stage with open
collector. Also included is a pair of complementary Schottky
diodes which, when shunted across the load, provide the
capability for symmetrical peak clipping.
The input stage is biased by an external 200 kΩ resistor. It is
important that this resistor be
±1%
tolerance for optimum
performance. An internal negative feedback loop ensures a
stable operating point for the output stage over the designed
operating voltage. Because of the lowered idle current,
trimming the output current with the use of a single external
resistor is not recommended for the LT505.
The typical gain for this IC is 74 Due to low power consumption
dB.
this part is the perfect choice for the output
stage of class A hearing instruments.
BLOCK DIAGRAM
V
MIC
8
2.2K
O/P
3
6
I/P
V
B
4
MPO
8
1
2.2 K
EQUIVALENT CIRCUIT
4
1
+
_
33K
100
5
200
6
3
27 K
100
33 K
2
200
7
GND
R
E
U.S. Patent No. 4,034,306
Patented in other countries
2
5
7
R
VC
All resistors in ohms, all capacitors in
µF
unless otherwise stated
Revision Date: June 1994
Document No. 500 - 45 - 9
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) 3247-8839
ABSOLUTE MAXIMUM RATINGS
PARAMETER
Supply Voltage
Power Dissipation
Operating Temperature Range
VALUE/UNITS
3 V DC
25 mW
-10°C to 40° C
V
B
O/P
R
E
MPO
CAUTION
CLASS 1 ESD SENSITIVITY
PIN CONNECTION
4
5
R
VC
I/P
GND
1
8
V
MIC
ELECTRICAL CHARACTERISTICS
All switches remain as shown in test circuit unless stated in conditions column. Conditions : V
CC
= 1.30 VDC , temperature 25˚ C
PARAMETER
Gain
Total Harmonic Dist.
Amplifier Current
Transducer Current
Total Current
Input Referred Noise
Volume Control Range
Battery Resist.Stability
Input Impedance (Pin 6)
Maximum Output
SYMBOL
CONDITIONS
V
OUT
= 200 mV
RMS
V
OUT
= 200 mV
RMS
MIN
70
-
44
130
174
-
TYP
74
2.0
53
210
263
1.4
47
-
15
0.240
MAX
78
5.0
62
260
322
2.2
-
-
-
0.310
UNITS
dB
%
µA
µA
µA
µV
RMS
dB
Ω
kΩ
V
RMS
I
A
I
L
I
A
+
I
L
R
VC
= 0 to 56.2 kΩ (S1 -ON/OFF)
R
B
= 22
Ω
36
22
-
V
I
N
= 0.5 m V
RMS
(S2 - closed)
0.165
V
B
= 1.3 VDC
R
B
= 4.7
S2
1.1
6K
V
O
+
2.2
200 k
8
4
2.2 K
3
6
HAMMOND
99966
1
R = 3.9 K
S
0.33
+
_
33 K
100
DOCUMENT
IDENTIFICATION
PRODUCT PROPOSAL
This data has been compiled for market investigation purposes
only, and does not constitute an offer for sale.
2
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 preproduction 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.
1 kHz
50Ω
+
10
R
S1
5
VC
200
7
= 56.2 K
All external resistors in ohms, all capacitors in
µF
unless otherwise stated
Fig. 1 Test Circuit
REVISION NOTES
Changes to Fig.1, test conditions, Pb/Sn 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 September 1982 Gennum Corporation. All rights reserved. Printed in Canada.
500-45-9
2
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