Document
HA12181FP
AM Radio Noise Reduction System
ADE-207-171A (Z) 2nd. Edition June 1997 Functions
• Buffer amp. for audio • Linear approximate circuit for noise reduction • IF Amp., detector, audio amp. and AGC circuit for noise detection • Gate pulse generator
Features
• High noise cancelling capacity: 46 dB typ. • Less gain loss: GV = –0.5 dB typ. • Low total harmonic destortion and high signal-to noise ratio: THD = 0.06% typ., S/N = 75 dB typ. • Operation supply voltage range: 7.0 V to 10 V (8.2 V typ.) • Less external parts count
HA12181FP
Block Diagram
R500 100 k IF AGC
+ C502 0.01µ 3.3µ Det. 1 14
C503 C504 0.22µ R502 22 k
12 15
R505 47 k AF AGC
Rev.2, Jun. 1997, page 2 of 21 IF AGC OR HPF1 LPF Pulse Det.(2)
(1) (2) 13
IF Input
16
Pulse Det.(1)
Gate pulse Gen.
IF Amp. LPF Det. Pulse Det. HPF AF Amp. AF AGC Noise AGC Stabi. Volt.
2nd IFT
4
ANT
7
SW2
SW1
1st IFT
C501 1000 p
VCC (8.2 V)
+
R506 12 k
SW4
Gate pulse (1) Gate pulse (2)
Phase Circuit
SW3
AF Input
Hight-pass Amp. (waveform compensation)
RF
MIX
IF
Det.
+ 3
Buffer Amp.
C506 100µ
C513 1µ
Stabilized Voltage Circuit 2 5 6 8 Level Diff. Det. Circuit Stabilized Current Circuit (waveform compensation)
OSC
SW5
AM-IC
10
9
11
C500 0.033µ
Capacitor for Pahse C512 0.068µ
Capacitor for Hold C511 0.033µ
AF Output Capacitor C509 + for By-pass R503 0.033µ 180 k C508 C510 R504 0.033µ Capacitor 1µ 4.7 k for waveform compensation
Gate Time Constant C507 2200 p
Unit
R:Ω C:F
HA12181FP
Table of Pin Description and External Parts
External parts DC voltage (V) (No Function input) Equivalent circuit 2.7 Influence of External parts Smaller than recommended value Longer distortion of recover.
No. of pin Name 1
No. R500 C502
Larger than recom- recommended mended value value 100 K 3.3 µ Longer time to stabilize AGC.
IF AGC Time constant for IF AGC.
1
R500 100k
C502 3.3µ
+
2
Bias1
Bypass for voltage Stabi. Input of AF.
3.2
2
C500 0.033µ
C500
0.033 µ
—
Increased noise.
3
AF input
3.3
20k
C513
1µ
—
—
3 +
C513 AF IN
4
Bias2
Decide 1.3 the current of filter network. 3.3
5
R506
4
12 K
Cut off frequency of L·P·F and H·P·F shifted lower.
Cut off frequency of L·P·F and H·P·F shifted higher.
5
Phase Phase circuit
C512
0.068 µ
Must be used on the recommended value.
C512 0.068µ
Rev.2, Jun. 1997, page 3 of 21
HA12181FP
Table of Pin Description and External Parts (cont)
External parts DC voltage (V) (No Function input) Equivalent circuit Hold of level difference. 3.3 Influence of External parts Smaller than recommended value
No. of pin Name 6 Hold
No. C511
Larger than recom- recommended mended value value 0.033 µ
Must be used on the recommended value.
6
C511 0.033µ
7 8
GND HighPass.
GND High3.3 Pass AMP. (Waveform Compensation)
—
— C510
— 0.033 µ
—
—
Must be used on the recommended value.
8
C510 0.033µ
9
AF out Output of 3.3 AF
C508 R504
1µ 4.7 K
Output DC cut Output load
9
+
C508 1µ
R504 4.7k
10
Wave form
Wave3.3 form Compensati.