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
GENNUM [ GENNUM CORPORATION ]
