鈥?/div>
operates from 1.05 to 3 V
DC
STANDARD PACKAGING
鈥?8 pin MICROpac
鈥?8 pin PLID
廬
鈥?Chip (64 x 62 mils)
Au Bump
Internally, a series shunt voltage regulator produces a 0.94 V
DC regulated output voltage. This provides a bias for electret
microphones and permits circuit operations over a wide range
of supply voltages, 1.05 to 3 V
DC
for LP502 without any
degradation of electrical performances.
As compared to the LD502, the LP502 incorporates an
additional diode between the amplifier output and the AGC
filter point. This 鈥渁ttack diode鈥?is responsible for precharging
the AGC filter point, which enables quicker attack time and
helps to reduce the gain overshoot (during transients) that is
observed in the LD502 with certain combinations of AGC input
coupling and filter capacitors. However, with this diode
connected, some level of AGC is always present with higher
output levels even when the AGC input is disconnected.
Therefore the LP502 cannot be used as a 鈥減ure鈥?linear
amplifier.
GAIN SET
7
4
By using R
GT
(see test circuit) to vary the value of this current
controlled resistance, the amplifier gain and compression
threshold can be controlled over a range of 60 dB.
The AGC current is derived from a full wave rectifier driven by
a differential amplifier. The attack time of the AGC circuit is
fixed at less than 1 ms. The release time is adjustable from
40 to 500 ms by selecting the value of an external capacitor
(C3).
DESCRIPTION
The LP502 is a compression (AGC) preamplifier that consists
of a single-ended input inverting amplifier, with an internal
current controlled resistance connected between input and
output.
V
B
2
V
REG
VOLTAGE
REGULATOR
1
A IN
AMPLIFIER
A OUT
3
FULL WAVE
RECTIFIER
AGC IN
6
8
GND
5
AGC FILTER
BLOCK DIAGRAM
Patented 1985
Canada 1183580
Patent Pending Europe 83.300836.0
USA 4506169
Japan 58-06886
Document No. HP2802-1
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3
tel. (905) 632-2996 fax: (905) 632-5946
Gennum Japan Corporation:C-101 Mi yamae Vill age, 2鈥?0鈥?2 Mi yamae, Suginami鈥搆u, Tokyo
168-0081
, Japan tel. (03) 3334-7700 fax (03) 3247-8839
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