SAN2202
8 Measurement results & curves
8.1 Frequency response
Fig. 2 shows the frequency
response curve of the loudspeaker
amplifier. The curve shows the
output level on an 8Ω resistor
(solid line) and an 8Ω loudspeaker
(dotted line; PHILIPS AD3371
series 80mm∅ 8Ω speaker)
measured with maximum volume
and
-10dBm Rx level on line. The peak
at 200Hz is a resonant frequency
of the specific loudspeaker type.
Gain of the amplifier is set by the
resistors R6 and the attenuation of
VR1. The bandwidth is adjusted by
CC4.
Frequency response of LS-A plifier
m
-12
-13
Output level [dBm]
8 Ohm Resistor
-14
-15
-16
-17
-18
100
8 Ohm Loudspeaker
1000
f [Hz]
10000
Fig. 2:Frequency response of loudspeaker amplifier (P
Line
=-10dBm)
8.2 maximum sending level
Fig.3
shows
the
maximum
Transmit sending level, measured
at LI vs. line current, assuming a
total harmonic distortion (THD) of
less than 1%.
AN2201a (dotted line):
At line
currents >40mA, VPP will rise up to
2.5V (@ 90mA) and sending level
will be slightly distorted before it
reaches the soft clip level (± 2V
peak
) .
AN2202b (solid line):There
is no
influence in maximum sending
level, the transmit signal can be up
to the soft clip level at line currents
of >12mA.
max. sending level @ THD <1%
4,4
4,2
4
3,8
VLI [Vpp]
3,6
3,4
3,2
3
2,8
2,6
15
20
25
30
35
40
45
50
55
60
SAN2202a
SAN2202b
Line current [mA]
Fig. 3: maximum sending level vs. line current (@ THD <1%)
8.3 maximum output power
Fig.4 and Fig.5 show the maximum output power on an 8Ω loudspeaker at f=1kHz: the curves indicate the
maximum output power with <2% and <3% total harmonic distortion.
SAN2202a:
The lower output drive capability at higher line currents results from nonlinearities at higher collector
currents and mismatch in the complementary transistor types.
SAN2202b:
Maximum output power is not decreased with higher line currents.
6/9
sames
SAMES [ SAMES ]
