Why it
is important to use
a limiter?
Audio signals as
music or
speech have
big dynamic
ranges. There are
silent and loud sections.
These audio signals aren't
too good for
a
transmitter, which requires audio signal
with
constant level
on the input. Limiter
is a
device, which weakens
loud signals
and intensifies
silent signals.
On its output
there is signal with
constant level.
Technical specifications
Supply voltage: 10-14
V
stab.
Supply currents: 20 mA
Audio
input: impedance
20 kOhm, optional preemphasis
Output voltage:
0,4 V
rms
Dynamic
range: >50
dB
Output
voltage vs. input
voltage
Schematic diagram
Parts
list
Resistors:
R1 -
68 k
R2
-
22 k
R3 - 180
k
R4 -
10 M
R5 -
10 k
R6 - 47
R
R7
- 240
k
R8
- 1,5
k
R9 - 820
R
Capacitors:
C1 -
100 p (ceramic)
C2
- 1 n (plastic)
C3,
C6,
C12 -
100 n (ceramic)
C4,
C11, C13
- 100 u
(electrolytic)
C5
- 0,
33 u
(tantalum)
C7, C8
- 10 u (electrolytic)
C9 - 220 n
(plastic)
C10 -
47
n (ceramic)
C14 - 470
n
(plastic)
Misc.
:
T1 - BF245C
T2 -
BC556B, BC307
IC1
- LM386
PCB layout