LC502 データシートの表示（PDF） - Gennum -> Semtech
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LC502 Datasheet PDF : 5 Pages
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Low Voltage Cassette
Recorder Amplifier
LD502/LC507 APPLICATION NOTE
FEATURES
• Operation with supply voltages from as low as 1.1V
up to 6V
• Miniature packages available
• Greater than 40 dB AGC range in recording amplifier
provides for constant recording level over a wide
range of acoustic inputs
• Design flexibility permits minimum parts count
“economy” circuits or more sophisticated version
with broad smoother record/playback response
INTRODUCTION
This application note describes the use of three Gennum
integrated circuits, the LD502 and LC507 in recording/
playback amplifiers for battery operated cassette recorders
and dictaphones. A key feature of the circuits is their
ability to provide excellent performance by a single battery
cell. The LD502 is available in miniature MINIpac package.
The LC507 is packaged in a single in-line MICROpac M4.
1. GENERAL PURPOSE RECORDING AMPLIFIER
CIRCUIT DESCRIPTION
All the circuits described in this note comprise two gain
blocks. The first block utilizes the LD502 as a microphone
AGC preamplifier during recording or as a frequency
compensating preamp on playback. The second block
employs the LC507 as a record head driver during record-
ing and as a headset driver on playback.
The microphone AGC preamplifier requires only six exter-
nal components including the input and ouput coupling
capacitors. The initial gain is set by selecting the value of
R1. With R1=130kΩ the gain is typically 40 dB for input
levels up to the threshold (typically 80-100µV).
For input levels higher than the threshold, the AGC starts
operating and controls the gain maintaining the output
level at typically 10 mV.
+ C5
22
0.95V
1
+
IN
VCC
LD502
VR
Gain
Set
OUT
R1
130k
+ C4 R6
22 470
4
2k
C1
2.2
AGC AGC
GND Filter IN
C6 R2
1.0 5.6k
A
+
C2 +
2.2
C3
1.0
All resistors in ohms, all capacitors in farads unless otherwise stated
VCC
Bias
LC507
RC
C8
2
B 1.0
+
R4
27k
RF
C7
2.2nF
C9
2.2nF
3
RD
R3
Fig. 1 Circuit No. 1 General Purpose
Recording Amplifier
Revision Date: June 1994
Document No. 500 - 64 - 4
GENNUM CORPORATION P.O. Box 489, Stn A, Burlington, Ontario, Canada L7R 3Y3 tel. (905) 632-2996 fax: (905) 632-5946
Japan Branch: B-201, Miyamae Village, 2-10-42 Miyamae, Suginami-ku, Tokyo 168, Japan tel. (03) 3334-7700 fax: (03) 3247-8839
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