Class A Amplifier with
3 Gain Blocks & Schottky Diodes
LS509DATASHEET
DESCRIPTION
FEATURES
• 140 µA typical current drain
• low noise and distortion
TheLS509isaClassAamplifierutilizingGennum’sproprietary
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.
• 1.0 to 5 VDC operating range
• independent preamplifier
• 2 DC coupled stages
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
feedbackresistortothesourceimpedance. It isrecommended
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.
• class A output stage
• variable transducer current
• Schottky diodes for MPO control
• 4 kΩ microphone decoupling resistor
STANDARD PACKAGING
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
• 10 pin PLID®
• 10 pin SLT
• Chip (61 x 55 mils)
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
7
R
MIC
MPO
9
21k
A I/P
A
-
B
C
-
-
C O/P
6
10
R
E
2
R
E
1
3
5
4
A O/P B I/P
B O/P
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