A
V
MIC
R
MIC
A
IN
A
OUT
B
IN
GND
C
OUT
V
B
3
2
4
5
78
9
R
P1
B
C
61
10
B
OUT
R
MPO
C
IN
R
P2
FEATURES
• designed to drive Class D integrated receivers
• adjustable peak clipper
• low current drain
• low noise and distortion
• low external parts count
• two low noise preamplifiers
• transconductance output stage
• mid supply referenced output
• preamp A for Gain Trim or Telecoil
Low Current Preamplifier
with Output Limiting
DESCRIPTION
The GK504 is Gennum’s proprietary low current preamplifier
designed to drive the Class D series receivers. It consists of
two independent single-ended, low noise inverting amplifiers,
a symmetrical peak clipping, mid-supply referenced,
transconductance output stage, and an on-chip microphone
decoupling resistor.
Blocks A and B typically have an open loop voltage gain of
53 dB, with the closed loop gain set by the ratio of the feedback
resistor to 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. It is
acceptable to DC-couple blocks A and B of the device,
however the third stage must be AC coupled in order to
maintain DC bias requirements.
The major advantage of the GK504 over other preamplifiers is
the electronic MPO adjustment. Since conventional MPO is
not possible in the class D receivers, it is provided electronically.
The maximum output swing is easily set using an R
MPO
resistor.
The receiver output level is thus limited, preventing it from
exceeding the discomfort level.
Document No. 520 - 47 - 05
BLOCK DIAGRAM
STANDARD PACKAGING
• 10 pin MICROpac
• 10 pin PLID
®
• 10 pin SLT
• Chip ( 56 x 84 mils)
Au Bump
U.S. Patent No.07/354,327
GK504 - DATA SHEET
Revision Date; May 1998
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