|TEA1069N||Versatile speech/dialler/ringer with music-on-hold|
|TEA1069N Datasheet PDF : 44 Pages |
Versatile speech/dialler/ringer with
MICROPHONE INPUTS MIC+ AND MIC− AND GAIN PINS GAS1 AND GAS2
The circuit has symmetrical microphone inputs. Its input impedance is 64 kΩ (2 × 32 kΩ) and its voltage gain is typically
52 dB (when R7 = 68 kΩ). Dynamic, magnetic, piezoelectric or electret (with built-in FET source followers) microphones
can be used. Microphone arrangements are illustrated in Fig.7.
handbook, full pagewidth
a. Magnetic or dynamic
b. Electret microphone.
4 (42) MIC+
3 (41) MIC−
c. Piezoelectric microphone.
Pin numbers in parenthesis refer to the TEA1069H and TEA1069AH.
(1) Resistor may be connected to reduce the terminating impedance.
Fig.7 Alternative microphone arrangements.
The gain of the microphone amplifier can be adjusted
between 44 dB and 52 dB to suit the sensitivity of the
transducer in use. The gain is proportional to the value of
R7 which is connected between GAS1 and GAS2. Stability
is ensured by two external capacitors, C6 connected
between GAS1 and SLPE and C17 connected between
GAS1 and VEE. The value of C6 is 100 pF but this may be
increased to obtain a first-order low-pass filter. The value
of C17 is 10 times the value of C6. The cut-off frequency
corresponds to the time constant R7 × C6.
RECEIVING AMPLIFIER IR, QR AND GAR
The receiving amplifier has one input (IR) and one output
(QR). Earpiece arrangements are illustrated in Fig.8.
The IR to QR gain is typically 31 dB (when R4 = 100 kΩ).
It can be adjusted between 20 and 31 dB to match the
sensitivity of the transducer in use.
The gain is set with the value of R4 which is connected
between GAR and QR. The overall receive gain, between
LN and QR, is calculated by subtracting the anti-sidetone
network attenuation (32 dB) from the amplifier gain.
Two external capacitors, C4 and C7, ensure stability. C4 is
normally 100 pF and C7 is 10 times the value of C4.
The value of C4 may be increased to obtain a first-order
low-pass filter. The cut-off frequency will depend on the
time constant R4 × C4.
The output voltage of the receiving amplifier is specified for
continuous-wave drive. The maximum output voltage will
be higher under speech conditions where the peak to RMS
ratio is higher.
1998 Jan 08
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