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Low Distortion AGC Compression Amplifier
LP502 CUSTOM DATA SHEET
FEATURES * adjustable gain from 0 to 60 dB * 0.94 V DC voltage regulator on-chip * attack time fixed at less than 1 ms * release time adjustable from 40 to 500 ms * low input referred noise 1.2 V * <1 % distortion at 10 mVRMS output * operates from 1.05 to 3 VDC STANDARD PACKAGING * 8 pin MICROpac * 8 pin PLID (R) * 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 VDC 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 "attack diode" 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 "pure" linear amplifier.
GAIN SET 7 4
By using RGT (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.
VB
2 VREG
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, 2-10-42 Mi yamae, Suginami-ku, Tokyo 168-0081, Japan tel. (03) 3334-7700 fax (03) 3247-8839
ABSOLUTE MAXIMUM RATINGS
PARAMETER Supply Voltage Power Dissipation Operating Temperature Range Storage Temperature Range VALUE/UNITS 3 V DC 25 mW -10C to 50 C -20C to 70 C GAIN SET A OUT VREG A IN
PIN CONNECTION
4
5
AGC FILTER AGC IN VB
1
8
GND
CAUTION CLASS 1 ESD SENSITIVITY
ELECTRICAL CHARACTERISTICS
Conditions: Frequency = 1 kHz, Temperature = 25C, Supply Voltage V B = 1.3 VDC
PARAMETER Gain
SYMBOL AV
CONDITIONS VOUT = 11.0 mV, 20 Log ( V OUT V IN )
MIN 38
TYP 41
MAX 46
UNITS dB
Output Level Distortion -Linear - AGC Input Referred Noise Compression Function Ratio Total Amplifier Current Regulated Voltage Supply Rejection
VOHIGH THD
VIN = 6.32 mV, S1 closed VOUT = 11.0 mV VIN = 6.32mV, S1 closed
7.5 2 160 0.890 51
12 1 1 1.2 5 310 0.940 60
15.5 2.9 2.2 2.2 8 380 0.990 -
mV % % V dB A VDC dB
IRN
S2 closed,NFB 0.2 to 10 kHz at 12 dB/Oct
VIN = 0.1 to 6.32 mV, S1 closed IAMP VREG PSRR
All parameters and switches remain as shown in Test Circuit unless otherwise stated in "Conditions" column ITOT RGT 130k VB= 1.3 VDC
7
4
2
VOLTAGE REGULATOR C5 1.0 RTH 0 VOUT
C1 0.47
1
3
AMP
RS= 3.5k FULL WAVE RECTIFIER
6
S1
RL 10K
S2 RM 33K C2 1.0 VIN
C4 0.1
8 5
C3 1.0
All resistors in ohms, all capacitors in microfarads unless otherwise stated
Fig. 1 Test Circuit
HP2802-1
2
GAIN TRIM 4.7 500k
7 2
VB=1.3 VDC 4.7
4
LP502
4 1
4.7 0.1
VOLTAGE REGULATOR
LC549 6
5
VC =10k 0.1
2
1
AMP
3
RL=400 TYP
8
RS 3.9k FULL WAVE RECTIFIER
8 5
0.1
6 3 7
NC 0.047 0.1-1.0
All resistors in ohms, all capacitors in microfarads unless otherwise stated
Fig. 2 LP502/LC549Hearing Instrument Application
GAIN TRIM VB=1.3 VDC 500k 7 4.7 0.1 AMP 1 RS 3.9k FULL WAVE RECTIFIER 8 5 RE=33 3 0.1 VC 10k 3 6 0.1 2 VOLTAGE REGULATOR 2 0.1 33k 5 2k 4 8 1 7 18k 13.5k
LP502
4
LE507
25k
BK1606 Z=1k
6
0.47
All resistors in ohms, all capacitors in microfarads unless otherwise stated
Fig. 3 LP502/LE507 Hearing Instrument Application
3
HP2802-1
100
100
RTH=50k
OUTPUT (mV)
RTH=22k RTH=10k 10 RTH=0k
10
OUTPUT (mV)
1
RGT=130k RGT=82k RGT=68k RGT=47k
1 0.01
0.1
1.0
10
0.1 0.01
0.1
1.0
10
INPUT (mV)
INPUT (mV)
Fig. 4 I/O Characteristics at Various RTH Values
Fig. 5 I/O Characteristics at Various RGT Values
100
4 2 0 CS=0.22 F CS=0.1 F
RELATIVE OUTPUT (dB)
RTH=0
-2 -4 -6 -8 -10 -12 -14 -16 -18
OUTPUT (mV)
VB=3 VDC 10 VB=1.3 VDC
CS=0.047 F CS=0.033 F
0.1 0.01
0.1
1.0
10
-20 20
200
2K
20k
INPUT (mV)
FREQUENCY (Hz)
Fig. 6 Effects of Supply Voltage Variation
Fig. 7 Frequency Response at Various CS Values
4.0
3.0
THD (%)
2.0
DOCUMENT IDENTIFICATION
PRODUCT PROPOSAL This data has been compiled for market investigation purposes only, and does not constitute an offer for sale. ADVANCE INFORMATION NOTE This product is in development phase and specifications are subject to change without notice. Gennum reserves the right to remove the product at any time. Listing the product does not constitute an offer for sale. PRELIMINARY DATA SHEET The product is in a preproduction phase and specifications are subject to change without notice. DATA SHEET The product is in production. Gennum reserves the right to make changes at any time to improve reliability, function or design, in order to provide the best product possible.
1.0
0.0 0.0 5.0 10.0 15.0 20.0 25.0
OUTPUT (mV)
Fig. 8 Total Harmonic Distortion vs Output Level
Gennum Corporation assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. (c) Copyright August 1997 Gennum Corporation. All rights reserved. Printed in Canada.
HP2802-1
4

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