GC509 Datasheet, PDF (1/4 Pages) Gennum Corporation – Class A Amplifier with 3 Independent Gain Blocks

FEATURES
• 145 µA typical current drain
• low noise and distortion
• 1.0 to 5 VDC operating range
• 2 independent preamplifiers
• Class A output stage
• variable transducer current
• 4 kΩ microphone decoupling resistor
STANDARD PACKAGING
• 10 pin MICROpac
• 10 pin PLID ^®
• 10 pin SLT
• Chip (61 x 55 mils)
Au Bump
Class A Amplifier with
3 Independent Gain Blocks
GC509 DATA SHEET
DESCRIPTION
The GC509 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, and an on-chip microphone decoupling resistor.
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 GC509 is a Class A current drive.
It has a fixed reference voltage of typically 55 mV at pin 8
of the device. The current that flows in the transducer is the
ratio of the 55 mV reference voltage and the on-chip emitter
resistor (R_E). To increase the bias current in the transducer,
simply place an external R_E resistor from pin 8 to ground,
thereby decreasing the equivalent emitter resistance and
increasing the current.
V_B
5 ^RMIC
6
V_MIC
4
A IN
-A
-B
21K
-C
C OUT
7
8 ^RE
R_E
2
3
A OUT B IN
10
9
B OUT C IN
1
GND
All resistors in ohms, all capacitors in Farads unless otherwise
stated
BLOCK DIAGRAM
Document No. 510 - 70 - 3
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. [phone] fax: [phone]
Japan Branch: A-302, M i yamae Vi l l age, 2–10–42 M i yamae, Suginami–ku, Tokyo 168, Japan tel. [phone] fax [phone]