SAN2202 Просмотр технического описания (PDF) - South African Micro Electronic Systems

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SAN2202

SINGLE CHIP “SPEAKERPHONE” WITH 8 - OHM LOUDSPEAKER AMPLIFIER

South African Micro Electronic Systems 

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.

-12

-13

-14

-15

-16

-17

-18

100

Frequency response of LS-Amplifier

8 Ohm Resistor

8 Ohm Loudspeaker

1000

f [Hz]

10000

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 (± 2Vpeak

).

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.

Fig. 2:Frequency response of loudspeaker amplifier (PLine=-10dBm)

max. sending level @ THD <1%

4,4

4,2

4

3,8

3,6

3,4

3,2

3

SAN2202a

2,8

SAN2202b

2,6

15 20 25 30 35 40 45 50 55 60

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

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